Piezoelectric element, ink jet head, angular velocity sensor, manufacturing method thereof, and ink jet type recording apparatus

ABSTRACT

In a piezoelectric element, an adhesive layer  12  is provided on a substrate  11 , a first electrode layer  14  made of a noble metal containing titanium or titanium oxide is provided on the adhesive layer  12 , and an orientation control layer  15  that is preferentially oriented along a (100) or (001) plane is provided on the first electrode layer  14 . In the vicinity of a surface of the orientation control layer  15  that is closer to the first electrode layer  14 , a (100)- or (001)-oriented region extends over titanium or titanium oxide located on one surface of the first electrode layer  14  that is closer to the orientation control layer  15 , and the cross-sectional area of the region in the direction perpendicular to the thickness direction gradually increases in the direction away from the first electrode layer  14  toward the opposite side. Further, a piezoelectric layer  16  that is preferentially oriented along a (001) plane is provided on the orientation control layer  15.

TECHNICAL FIELD

The present invention relates to a piezoelectric element having anelectro-mechanical conversion function, an ink jet head using thepiezoelectric element, an angular sensor, a method for manufacturing thesame, and an ink jet recording apparatus including the ink jet head asprinting means.

BACKGROUND ART

Generally, a piezoelectric material is a material capable of convertinga mechanical energy to an electrical energy and vice versa. A typicalexample of a piezoelectric material is lead zirconate titanate having aperovskite crystalline structure (Pb(Zr,Ti)O₃) (hereinafter referred toas “PZT”). In PZT, the greatest piezoelectric displacement is obtainedin the <001> direction (the c axis direction) in the case of atetragonal system, and in the <111> direction in the case of arhombohedral system. However, many of the piezoelectric materials arepolycrystals made up of a collection of crystal grains, and thecrystallographic axes of the crystal grains are oriented randomly.Therefore, the spontaneous polarizations Ps are also arranged randomly.

Along with the recent downsizing of electronic appliances, there is astrong demand for reducing the size of piezoelectric elements using apiezoelectric material. In order to meet the demand, more piezoelectricelements are already used in the form of thin films whose volumes can besignificantly reduced from those of sinters, which have conventionallybeen used in various applications, and active researches anddevelopments have been made for reducing the thickness of thin-filmpiezoelectric elements. For example, in the case of tetragonal PZT, thespontaneous polarization Ps is oriented in the c axis direction.Therefore, in order to realize superior piezoelectric characteristicseven with a reduced thickness, the c axes of crystal grains forming aPZT thin film need to be aligned vertical to the substrate plane. Inorder to realize such an alignment, a sputtering method has been used inthe prior art. Specifically, on a single crystal substrate made ofmagnesium oxide (MgO) having an NaCl-type crystalline structure, whichhas been cut out so that the surface thereof is along the crystalorientation of the (100) plane, a (100)-oriented Pt electrode thin filmis formed as a lower electrode on the substrate, and a PZT thin filmwhose c axis is oriented vertical to the surface of the Pt electrode isformed on the Pt electrode at a temperature of 600 to 700° C. (see, forexample, Journal of Applied Physics vol. 65 No. 4 (published on 15 Feb.1989 from the American Physical Society) pp. 1666–1670, and JapaneseUnexamined Patent Publication No. 10-209517). In such a case, if apiezoelectric element layer having a thickness of 0.1 μm and made ofPbTiO₃ or (Pb,La)TiO₃, free of Zr, is formed as a base layer for a PZTthin film on the (100)-oriented Pt electrode before the formation of aPZT thin film, and then a PZT thin film having a thickness of 2.5 μm isformed on the piezoelectric element layer by a sputtering method, it isless likely that a layer of a low crystallinity made of a Zr oxide isformed early in the formation of the PZT thin film, thereby obtaining aPZT thin film having a higher crystallinity. Specifically, a PZT thinfilm whose degree of (001) orientation (“α(001)”) is about 100% isobtained.

Herein, α(001) is defined as follows:α(001)=I(001)/ΣI(hkl).

ΣI(hkl) is the sum of diffraction peak intensities from various crystalplanes of PZT having a perovskite crystalline structure for a Cu-Kα 2θrange of 10° to 70° in an X-ray diffraction method. Note that the (002)plane and the (200) plane are not included in ΣI(hkl) as they areequivalent to the (001) plane and (100) plane.

However, this method uses an MgO single crystal substrate as a basesubstrate, thereby increasing the cost of a piezoelectric element, andthus the cost of an ink jet head using the piezoelectric element.Moreover, another drawback is that the variety of the substrate materialis limited to the MgO single crystal.

In view of this, various methods have been developed for forming a(001)- or (100)-oriented film of a perovskite piezoelectric materialsuch as PZT on an inexpensive substrate such as a silicon substrate. Forexample, Japanese Patent Publication No. 3021930 discloses that a PZTfilm that is preferentially oriented along the (100) plane can beproduced by applying a precursor solution of PZT or lanthanum-containingPZT on a (111)-oriented Pt electrode, performing a thermal decompositionprocess at 450 to 550° C. before the precursor solution is crystallizedand then heating and crystallizing the precursor solution at 550 to 800°C. (a sol-gel method).

Moreover, Japanese Unexamined Patent Publication No. 2001-88294discloses that by forming a very thin titanium layer on an iridium lowerelectrode, it is possible to control the crystal orientation of a PZTfilm to be formed thereon. This manufacturing method includes: forming abase layer whose main component is zirconium oxide on a substrate madeof silicon, or the like; forming a lower electrode containing iridium onthe base layer; depositing a very thin titanium layer on the lowerelectrode; forming an amorphous piezoelectric precursor thin filmcontaining metal element and oxygen element, which forms a ferroelectrichaving piezoelectric characteristics, on the titanium layer; and heatingand crystallizing the amorphous thin film at a high temperature (asol-gel method), thereby turning the amorphous thin film into aperovskite piezoelectric thin film. With this manufacturing method, thecrystal orientation of the piezoelectric thin film such as PZT can becontrolled by the thickness of the titanium layer, and a (100)-orientedfilm is obtained when the thickness of the titanium layer is set to be 2to 10 nm.

Furthermore, Japanese Unexamined Patent Publication No. 11-191646discloses that where a piezoelectric thin film is formed by using asol-gel method, a (100)-oriented PZT film can be obtained by forming atitanium layer having a thickness of 4 to 6 nm on a (111)-oriented Ptelectrode and using titanium oxide, which is formed through oxidizationof titanium in the titanium layer, as a nucleus.

However, while the methods described above are desirable methods that donot use an expensive MgO single-crystal substrate, it is difficult toobtain a well-oriented film having a desirable crystallinity in the filmformation process, as in the case of forming a piezoelectric thin filmon an MgO single-crystal substrate, because the piezoelectric thin filmis formed by a sol-gel method. In view of this, an amorphouspiezoelectric thin film is first formed, and then the layered structureincluding the substrate and the piezoelectric thin film is subjected toa heat treatment, so that the crystallographic axes are preferentiallyoriented in a desirable direction.

Moreover, when piezoelectric elements are mass-produced with a sol-gelmethod, the amorphous piezoelectric precursor thin film is likely to becracked due to changes in the volume during the degreasing step ofremoving organic substances. Furthermore, in the step of heating andcrystallizing the amorphous piezoelectric precursor thin film at a hightemperature, the film is likely to be cracked or peeled off from thelower electrode due to crystal changes.

As a solution to these problems with a sol-gel method, JapaneseUnexamined Patent Publication Nos. 2000-252544 and 10-81016 disclosethat it is effective to add titanium or titanium oxide in the lowerelectrode. Particularly, Japanese Unexamined Patent Publication No.10-81016 shows that a (100)-oriented PZT film can be obtained even witha sputtering method. Note however that a perovskite PZT film is notobtained directly on the lower electrode. First, a PZT film having anamorphous or pyrochlore crystalline structure is formed at a lowtemperature of 200° C. or less, which is then crystallized through aheat treatment at a high temperature of 500 to 700° C. in an oxygenatmosphere. Therefore, as with a sol-gel method, the film is likely tobe cracked or peeled off from the lower electrode due to crystal changesin the step of heating and crystallizing the film at a high temperature.Moreover, the degree of (001) orientation or the degree of (100)orientation of the PZT film formed by a sol-gel method or a sputteringmethod as described above is 85% or less with either method.

Furthermore, with a sol-gel method, the maximum thickness of the PZTfilm to be formed in a single iteration of the step (including theapplication of the precursor solution and the following heat treatment)is about 100 nm at maximum. Therefore, in order to obtain a thickness of1 μm or more, which is required for a piezoelectric element, it isnecessary to repeat this step ten times or more, whereby the productionyield may be reduced.

On the other hand, according to Japanese Unexamined Patent PublicationNo. 2001-88294, supra, states that attempts were made to control theorientation of PZT on an Ir base electrode with a very thin titaniumlayer formed thereon by using a method other than a sol-gel method(including an MOD method) (in which an amorphous thin film is onceformed and then the thin film is turned into a crystalline thin filmthrough an aftertreatment such as a heat treatment), i.e., by using amethod in which a crystalline thin film is directly formed without thecrystallization step using a heat treatment, e.g., a sputtering method,a laser ablation method or a CVD method, and that a well-oriented filmwas not obtained with any method other than a sol-gel method. The reasonis stated to be as follows. The crystallization of the PZT film proceedsgradually from the lower electrode side to the upper electrode side witha sol-gel method, whereas with a CVD method or a sputtering method, thecrystallization of the PZT film proceeds randomly, resulting inirregular crystallization, and thus making the orientation controldifficult.

Moreover, when a titanium oxide film whose thickness is 12 nm or less isformed on a (111)-oriented Pt electrode layer, and a lead titanate filmor a PZT film having a perovskite crystalline structure is formeddirectly by a sputtering method, either film exhibits a (111)orientation property, and a (100)- or (001)-oriented film is notobtained (see Journal of Applied Physics vol. 83 No. 7 (published on 1Apr. 1998 from the American Physical Society) pp. 3835–3841).

The present invention has been made in view of the above, and has anobject to provide a reliable piezoelectric element with desirablepiezoelectric characteristics at low cost.

DISCLOSURE OF INVENTION

In order to achieve the object set forth above, according to the presentinvention, an electrode layer is made of a noble metal containingtitanium or titanium oxide, an orientation control layer is formed onthe electrode layer, and a piezoelectric layer is formed on theorientation control layer. In the formation of the orientation controllayer, titanium or titanium oxide located on a surface of the electrodelayer that is closer to the orientation control layer is used as anucleus to perform crystal growth over the titanium or titanium oxide,such that the orientation control layer is preferentially oriented alongthe (100) or (001) plane, and the piezoelectric layer is preferentiallyoriented along the (001) plane by the orientation control layer.

Specifically, the 1st invention is directed to a piezoelectric elementincluding a first electrode layer provided on a substrate, anorientation control layer provided on the first electrode layer, apiezoelectric layer provided on the orientation control layer, and asecond electrode layer provided on the piezoelectric layer.

The first electrode layer is made of a noble metal containing titaniumor titanium oxide. The orientation control layer is made of a cubic ortetragonal perovskite oxide that is preferentially oriented along a(100) or (001) plane. The piezoelectric layer is made of a rhombohedralor tetragonal perovskite oxide that is preferentially oriented along a(001) plane. In the vicinity of one surface of the orientation controllayer that is closer to the first electrode layer, a (100)- or(001)-oriented region extends over titanium or titanium oxide located onone surface of the first electrode layer that is closer to theorientation control layer, and the cross-sectional area of the (100)- or(001)-oriented region in the direction perpendicular to the thicknessdirection gradually increases in the direction away from the firstelectrode layer toward the piezoelectric layer.

In the above structure, titanium or titanium oxide is added to the noblemetal film which is employed as the first electrode layer, whereby theadhesion between the substrate and the first electrode layer isimproved, and peeling off during the manufacture of the piezoelectricelement is prevented. Further, in the case where the orientation controllayer is formed on the first electrode layer by a sputtering method, theorientation control layer is likely to be oriented along the (100) or(001) plane (the (100) plane and the (001) plane are the same in a cubicsystem) even if the first electrode layer is oriented along the (111)plane. Titanium or titanium oxide exists in a dotted pattern on onesurface of the first electrode layer, and the titanium or titanium oxideis used as a nucleus to grow the orientation control layer over thetitanium or titanium oxide. Thus, the orientation control layer islikely to be oriented along the (100) or (001) plane over the titaniumor titanium oxide. Furthermore, since the titanium or titanium oxide iscontained in the first electrode layer, the titanium or titanium oxidehardly protrudes above the surface of the first electrode layer (even ifit protrudes, the amount of protrusion is smaller than 2 nm). Also forsuch a reason, the orientation control layer is likely to be orientedalong the (100) or (001) plane. On the other hand, the first electrodelayer is normally oriented along the (111) plane when a siliconsubstrate, or the like, is used. Therefore, a region of the orientationcontrol layer above a portion of the surface of the first electrodelayer where none of titanium and titanium oxide exist may be oriented ina direction other than along the (100) or (001) plane (e.g., along the(111) plane) or may be amorphous. However, such a region that is notoriented along the (100) or (001) plane extends only in the vicinity ofthe surface of the orientation control layer that is closer to the firstelectrode layer (i.e., within a distance of about 20 nm at maximum fromthe surface). Therefore, a (100)- or (001)-oriented region which extendsover titanium or titanium oxide expands as the crystal growth processproceeds, and the cross-sectional area of the (100)- or (001)-orientedregion in the direction perpendicular to the thickness directiongradually increases in the direction away from the first electrode layertoward the opposite side (the piezoelectric layer), while the regionthat is not oriented along the (100) or (001) plane gradually shrinks.When the thickness of the orientation control layer is about 20 nm, the(100)- or (001)-oriented region extends substantially across the entiresurface. In the case where the piezoelectric layer is formed on thethus-formed orientation control layer, the piezoelectric layer isoriented by the orientation control layer along the (001) plane(including the (100) plane in a rhombohedral system because the (100)plane and the (001) plane are the same in a rhombohedral system). Whensuch an orientation control layer is provided, a material which canfurther improve the crystallinity and orientation property can be usedfor the orientation control layer, while a piezoelectric material havingdesirable piezoelectric characteristics is used for the piezoelectriclayer. As a result, the degree of (001) orientation of the piezoelectriclayer can be set to 90% or more. It should be noted that, in theorientation control layer, the region that is not oriented along the(100) or (001) plane may exist not only in the vicinity of the surfaceof the orientation control layer that is closer to the first electrodelayer but also on a surface of the orientation control layer that iscloser to the piezoelectric layer. Even in such a case, the (100)- or(001)-oriented region extends substantially across the entire surface ofthe orientation control layer that is close to the piezoelectric layerso long as the thickness of the orientation control layer is 0.01 μm ormore, and as a result, the degree of (001) orientation of thepiezoelectric layer is 90% or higher.

Therefore, even with a deposition method, other than a sol-gel method,in which a crystalline thin film is directly formed on an inexpensivesubstrate such as a silicon substrate without the crystallization stepusing a heat treatment (e.g., a sputtering method or a CVD method), itis possible to obtain a piezoelectric layer with a desirableorientation, whereby it is possible to suppress the deviation in thepiezoelectric characteristics of the piezoelectric element and toimprove the reliability thereof. As the piezoelectric element is usedwhile applying an electric field in the direction vertical to thesurface of the piezoelectric layer thereof, the (001) orientation isadvantageous, particularly with a tetragonal perovskite PZT film,because the direction of the electric field is then parallel to the<001> polarization axis direction, thus resulting in an increasedpiezoelectric effect. Moreover, since the polarization rotation due tothe application of an electric field does not occur, it is possible tosuppress the deviation in the piezoelectric characteristics of thepiezoelectric element and to improve the reliability thereof. On theother hand, with a rhombohedral perovskite PZT film, since thepolarization axis extends in the <111>direction, the (100) orientationresults in an angle of about 54° between the direction of the electricfield and the direction of the polarization axis. Nevertheless, byimproving the (100) orientation property, the polarization can keep aconstant angle with respect to the electric field application.Therefore, also in this case, the polarization rotation due to theelectric field application does not occur, whereby it is possible tosuppress the deviation in the piezoelectric characteristics of thepiezoelectric element and to improve the reliability thereof (forexample, in a non-oriented PZT film, the polarization axes are orientedin various directions, and application of an electric field urges thepolarization axes to be aligned parallel to the electric field, wherebythe piezoelectric characteristics may become voltage dependent and varysignificantly, or a sufficient reliability may not be maintained due toaging).

Moreover, a piezoelectric layer having a desirable orientation is easilyobtained without using an expensive MgO single-crystal substrate.Therefore, it is possible to reduce the manufacturing cost by using aninexpensive substrate, such as a glass substrate, a metal substrate, aceramic substrate or an Si substrate.

Furthermore, even if the thickness of the piezoelectric layer is 1 μm ormore, it is not necessary to repeat the same step a number of times, aswith a sol-gel method, and the piezoelectric layer can be formed easilyby a sputtering method, or the like. Thus, it is possible to suppress adecrease in the production yield.

According to the 2nd invention, in the 1st invention, the orientationcontrol layer is made of lead lanthanum zirconate titanate whosezirconium content is equal to or greater than zero and less than orequal to 20 mol % and whose lead content is in excess of thestoichiometric composition by an amount greater than zero and less thanor equal to 30 mol %, or made of the lead lanthanum zirconate titanateto which at least one of magnesium and manganese is added.

By using such a lead lanthanum zirconate titanate material (PLZT;including the composition where the zirconium content is zero, i.e.,lead lanthanum titanate (PLT)) for the orientation control layer, theorientation control layer is even more likely to be oriented along the(100) or (001) plane, whereby it is possible to improve the orientationof the piezoelectric layer. In addition, by setting the zirconiumcontent to be less than or equal to 20 mol %, it is less likely that alayer of a low crystallinity made of a Zr oxide is formed early in thecrystal growth process. Furthermore, by setting the lead content to bein excess of the stoichiometric composition by an amount greater thanzero and less than or equal to 30 mol %, a decrease in the crystallinityof the orientation control layer is reliably suppressed, whereby thebreakdown voltage is increased. Therefore, it is possible to reliablyimprove the crystallinity or the orientation of the piezoelectric layer,and to further improve the piezoelectric characteristics of thepiezoelectric element.

According to the 3rd invention, in the 2nd invention, the lanthanumcontent of the lead lanthanum zirconate titanate is greater than zeroand less than or equal to 25 mol %.

According to the 4th invention, in the 2nd invention, when at least oneof magnesium and manganese is added to the lead lanthanum zirconatetitanate, the total amount thereof to be added is greater than zero andless than or equal to 10 mol %. With the 3rd and 4th inventions, adecrease in the crystallinity of the orientation control layer is moreefficiently suppressed.

According to the 5th invention, in the 1st invention, the firstelectrode layer is made of at least one noble metal selected from thegroup consisting of platinum, iridium, palladium and ruthenium, and thecontent of the titanium or titanium oxide which is contained in thenoble metal is greater than zero and less than or equal to 30 mol %.

With such features, the first electrode layer sufficiently endure thetemperatures selected for forming the respective films of thepiezoelectric element by a sputtering method, or the like, and such amaterial of the first electrode layer is appropriate for use in theelectrode. Further, the content of titanium or titanium oxide ispreferably set to 30 mol % or less because, if it is higher than 30 mol%, the crystallinity and orientation property of the orientation controllayer (and hence the crystallinity and orientation property of thepiezoelectric layer) are deteriorated.

According to the 6th invention, in the 1st invention, titanium ortitanium oxide existing at a surface of the first electrode layer thatis closer to the orientation control layer protrudes less than 2 nm fromthe surface.

The titanium or titanium oxide is intended to be contained in the firstelectrode layer, but is not intended to be provided above the surface ofthe first electrode layer. Thus, the titanium or titanium oxide hardlyprotrudes above the surface of the first electrode layer that is closerto the orientation control layer. Even if it protrudes, the amount ofprotrusion is smaller than 2 nm. Therefore, as described above, theorientation control layer is likely to be oriented along the (100) or(001) plane.

According to the 7th invention, in the 1st invention, the piezoelectriclayer is made of a piezoelectric material whose main component is leadzirconate titanate.

With such a feature, the piezoelectric material has desirablepiezoelectric characteristics, and a piezoelectric element of highperformance can be obtained.

According to the 8th invention, in the 1st invention, an adhesive layerfor improving adhesion between the substrate and the first electrodelayer is provided between the substrate and the first electrode layer.

With such a feature, the adhesion between the substrate and the firstelectrode layer is further improved, and accordingly, peeling off duringthe manufacture of the piezoelectric element is surely prevented.

The 9th invention is directed to an ink jet head comprising: apiezoelectric element in which a first electrode layer, an orientationcontrol layer, a piezoelectric layer and a second electrode layer arelayered in this order; a vibration layer provided on one surface of thepiezoelectric element that is closer to the second electrode layer; anda pressure chamber member bonded to one surface of the vibration layerthat is away from the piezoelectric element and including a pressurechamber for storing ink therein, in which the vibration layer isdisplaced in a thickness direction by a piezoelectric effect of thepiezoelectric layer of the piezoelectric element so as to discharge theink out of the pressure chamber.

In this invention, the first electrode layer of the piezoelectricelement is made of a noble metal containing titanium or titanium oxide.The orientation control layer is made of a cubic or tetragonalperovskite oxide that is preferentially oriented along a (100) or (001)plane. The piezoelectric layer is made of a rhombohedral or tetragonalperovskite oxide that is preferentially oriented along a (001) plane. Inthe vicinity of one surface of the orientation control layer that iscloser to the first electrode layer, a (100)- or (001)-oriented regionextends over titanium or titanium oxide located on one surface of thefirst electrode layer that is closer to the orientation control layer,and the cross-sectional area of the (100)- or (001)-oriented region inthe direction perpendicular to the thickness direction graduallyincreases in the direction away from the first electrode layer towardthe piezoelectric layer.

According to this invention, the first electrode layer, the orientationcontrol layer, the piezoelectric layer, the second electrode layer, andthe vibration layer are formed in this order on a substrate by asputtering method, or the like. The pressure chamber member is thenbonded to the vibration layer, and thereafter, the substrate is removed.As a result, an ink jet head including a piezoelectric element which hasa similar structure to that of the 1st invention is obtained, with thedegree of (001) orientation of the piezoelectric layer being 90% ormore. Thus, an ink jet head having a desirable durability with a smalldeviation in the ink-discharge performance is obtained.

The 10th invention is directed to an ink jet head comprising: apiezoelectric element in which a first electrode layer, an orientationcontrol layer, a piezoelectric layer and a second electrode layer arelayered in this order; a vibration layer provided on one surface of thepiezoelectric element that is closer to the first electrode layer; and apressure chamber member bonded to one surface of the vibration layerthat is away from the piezoelectric element and including a pressurechamber for storing ink therein, in which the vibration layer isdisplaced in a thickness direction by a piezoelectric effect of thepiezoelectric layer of the piezoelectric element so as to discharge theink out of the pressure chamber.

The first electrode layer of the piezoelectric element is made of anoble metal containing titanium or titanium oxide. The orientationcontrol layer is made of a cubic or tetragonal perovskite oxide that ispreferentially oriented along a (100) or (001) plane. The piezoelectriclayer is made of a rhombohedral or tetragonal perovskite oxide that ispreferentially oriented along a (001) plane. In the vicinity of onesurface of the orientation control layer that is closer to the firstelectrode layer, a (100)- or (001)-oriented region extends over titaniumor titanium oxide located on one surface of the first electrode layerthat is closer to the orientation control layer, and the cross-sectionalarea of the (100)- or (001)-oriented region in the directionperpendicular to the thickness direction gradually increases in thedirection away from the first electrode layer toward the piezoelectriclayer.

According to this invention, the pressure chamber member is used as asubstrate, and the vibration layer, the first electrode layer, theorientation control layer, the piezoelectric layer and the secondelectrode layer are formed on the pressure chamber member in this orderby a sputtering method, or the like, whereby an ink jet head havingsimilar effects to those of the 9th invention is obtained.

The 11th invention is directed to an angular velocity sensor whichcomprises a substrate including a fixed portion and at least a pair ofvibrating portions extending from the fixed portion in a predetermineddirection, in which a first electrode layer, an orientation controllayer, a piezoelectric layer and a second electrode layer are layered inthis order at least on each of the vibrating portions of the substrate,and the second electrode layer on each of the vibrating portions ispatterned into at least one driving electrode for vibrating thevibrating portion in a width direction thereof and at least onedetection electrode for detecting a displacement of the vibratingportion in a thickness direction thereof.

The first electrode layer is made of a noble metal containing titaniumor titanium oxide. The orientation control layer is made of a cubic ortetragonal perovskite oxide that is preferentially oriented along a(100) or (001) plane. The piezoelectric layer is made of a rhombohedralor tetragonal perovskite oxide that is preferentially oriented along a(001) plane. In the vicinity of one surface of the orientation controllayer that is closer to the first electrode layer, a (100)- or(001)-oriented region extends over titanium or titanium oxide located onone surface of the first electrode layer that is closer to theorientation control layer, and the cross-sectional area of the (100)- or(001)-oriented region in the direction perpendicular to the thicknessdirection gradually increases in the direction away from the firstelectrode layer toward the piezoelectric layer.

According to this invention, each vibrating portion of the substrate isvibrated in the width direction thereof by applying a voltage betweenthe driving electrode of the second electrode layer and the firstelectrode layer. When the vibrating portion deforms in the thicknessdirection due to the Coriolis force while it is being vibrated, avoltage is generated between the detection electrode of the secondelectrode layer and the first electrode layer, whereby the angularvelocity can be calculated based on the magnitude of the voltage (theCoriolis force). The portion for detecting the angular velocity (thevibrating portion) is a piezoelectric element having a structure similarto that of the 1st invention. Therefore, the piezoelectric constant canbe increased to be about 40 times as large as that of a conventionalangular velocity sensor using quartz, and thus the size thereof can bereduced significantly. Moreover, even if the angular velocity sensorsare mass-produced industrially, it is possible to obtain angularvelocity sensors with a high characteristics reproducibility and a smallcharacteristics deviation, and with a high breakdown voltage and a highreliability.

According to the 12th invention, in the 11th invention, the orientationcontrol layer is made of lead lanthanum zirconate titanate whosezirconium content is equal to or greater than zero and less than orequal to 20 mol % and whose lead content is in excess of thestoichiometric composition by an amount greater than zero and less thanor equal to 30 mol %, or made of the lead lanthanum zirconate titanateto which at least one of magnesium and manganese is added. With thisfeature, the same effects as those of the 2nd invention are obtained.

According to the 13th invention, in the 12th invention, the lanthanumcontent of the lead lanthanum zirconate titanate is greater than zeroand less than or equal to 25 mol %. With this feature, the same effectsas those of the 3rd invention are obtained.

According to the 14th invention, in the 12th invention, when at leastone of magnesium and manganese is added to the lead lanthanum zirconatetitanate, the total amount thereof to be added is greater than zero andless than or equal to 10 mol %. With this feature, the same effects asthose of the 4th invention are obtained.

According to the 15th invention, in the 11th invention, the firstelectrode layer is made of at least one noble metal selected from thegroup consisting of platinum, iridium, palladium and ruthenium, and thecontent of the titanium or titanium oxide which is contained in thenoble metal is greater than zero and less than or equal to 30 mol %.With this feature, the same effects as those of the 5th invention areobtained.

According to the 16th invention, in the 11th invention, titanium ortitanium oxide existing at a surface of the first electrode layer thatis closer to the orientation control layer protrudes less than 2 nm fromthe surface. With this feature, the same effects as those of the 6thinvention are obtained.

According to the 17th invention, in the 11th invention, thepiezoelectric layer is made of a piezoelectric material whose maincomponent is lead zirconate titanate. With this feature, the sameeffects as those of the 7th invention are obtained.

According to the 18th invention, in the 11th invention, an adhesivelayer for improving adhesion between the substrate and the firstelectrode layer is provided between the substrate and the firstelectrode layer. With this feature, the same effects as those of the 8thinvention are obtained.

The 19th invention is directed to a method for manufacturing apiezoelectric element, which comprises the steps of: forming a firstelectrode layer made of a noble metal containing titanium or titaniumoxide on a substrate by a sputtering method; forming an orientationcontrol layer made of a cubic or tetragonal perovskite oxide on thefirst electrode layer by a sputtering method; forming a piezoelectriclayer made of a rhombohedral or tetragonal perovskite oxide on theorientation control layer by a sputtering method; and forming a secondelectrode layer on the piezoelectric layer.

In this invention, the step of forming the orientation control layerincludes a step of using titanium or titanium oxide which exists on onesurface of the first electrode layer that is closer to the orientationcontrol layer as a nucleus to perform crystal growth over the titaniumor titanium oxide such that the orientation control layer ispreferentially oriented along the (100) or (001) plane. The step offorming the piezoelectric layer includes a step of preferentiallyorienting the piezoelectric layer along the (001) plane by theorientation control layer.

With this invention, a piezoelectric element having the same effects asthose of the 1st invention can readily be manufactured.

The 20th invention is directed to a method for manufacturing an ink jethead, the ink jet bead including a piezoelectric element in which afirst electrode layer, an orientation control layer, a piezoelectriclayer and a second electrode layer are layered in this order, in which avibration layer is displaced in a thickness direction by a piezoelectriceffect of the piezoelectric layer of the piezoelectric element so as todischarge ink out of a pressure chamber.

The method of this invention includes the steps of: forming the firstelectrode layer made of a noble metal containing titanium or titaniumoxide on a substrate by a sputtering method; forming the orientationcontrol layer made of a cubic or tetragonal perovskite oxide on thefirst electrode layer by a sputtering method; forming the piezoelectriclayer made of a rhombohedral or tetragonal perovskite oxide by asputtering method; forming the second electrode layer on thepiezoelectric layer; forming the vibration layer on the second electrodelayer; bonding a pressure chamber member for forming the pressurechamber on one surface of the vibration layer that is away from thesecond electrode layer; and removing the substrate after the bondingstep. The step of forming the orientation control layer includes a stepof using titanium or titanium oxide which exists on one surface of thefirst electrode layer that is closer to the orientation control layer asa nucleus to perform crystal growth over the titanium or titanium oxidesuch that the orientation control layer is preferentially oriented alongthe (100) or (001) plane. The step of forming the piezoelectric layerincludes a step of preferentially orienting the piezoelectric layeralong the (001) plane by the orientation control layer.

With such features, an ink jet head having the same effects as those ofthe 9th invention can readily be manufactured.

The 21st invention is directed to a method for manufacturing an ink jethead, the ink jet head including a piezoelectric element in which afirst electrode layer, an orientation control layer, a piezoelectriclayer and a second electrode layer are layered in this order, in which avibration layer is displaced in a thickness direction by a piezoelectriceffect of the piezoelectric layer of the piezoelectric element so as todischarge ink out of a pressure chamber.

The method of this invention includes the steps of: forming thevibration layer on a pressure chamber substrate for forming the pressurechamber; forming the first electrode layer made of a noble metalcontaining titanium or titanium oxide on the vibration layer by asputtering method; forming the orientation control layer made of a cubicor tetragonal perovskite oxide on the first electrode layer by asputtering method; forming the piezoelectric layer made of arhombohedral or tetragonal perovskite oxide by a sputtering method;forming the second electrode layer on the piezoelectric layer; andforming the pressure chamber in the pressure chamber substrate. The stepof forming the orientation control layer includes a step of usingtitanium or titanium oxide which exists on one surface of the firstelectrode layer that is closer to the orientation control layer as anucleus to perform crystal growth over the titanium or titanium oxidesuch that the orientation control layer is preferentially oriented alongthe (100) or (001) plane. The step of forming the piezoelectric layerincludes a step of preferentially orienting the piezoelectric layeralong the (001) plane by the orientation control layer.

With such features, an ink jet head having the same effects as those ofthe 10th invention can readily be manufactured.

The 22nd invention is directed to a method for manufacturing an angularvelocity sensor, the angular velocity sensor comprising a substrateincluding a fixed portion and at least a pair of vibrating portionsextending from the fixed portion in a predetermined direction, in whicha first electrode layer, an orientation control layer, a piezoelectriclayer and a second electrode layer are layered in this order at least oneach of the vibrating portions of the substrate, and the secondelectrode layer on each of the vibrating portions is patterned into atleast one driving electrode for vibrating the vibrating portion in awidth direction thereof and at least one detection electrode fordetecting a displacement of the vibrating portion in a thicknessdirection thereof.

The method of this invention includes the steps of: forming the firstelectrode layer made of a noble metal containing titanium or titaniumoxide on a substrate by a sputtering method; forming the orientationcontrol layer made of a cubic or tetragonal perovskite oxide on thefirst electrode layer by a sputtering method; forming the piezoelectriclayer made of a rhombohedral or tetragonal perovskite oxide on theorientation control layer by a sputtering method; forming the secondelectrode layer on the piezoelectric layer; patterning the secondelectrode layer so as to form the driving electrode and the detectionelectrode; patterning the piezoelectric layer, the orientation controllayer and the first electrode layer; and patterning the substrate so asto form the fixed portion and the vibrating portions. The step offorming the orientation control layer includes a step of using titaniumor titanium oxide which exists on one surface of the first electrodelayer that is closer to the orientation control layer as a nucleus toperform crystal growth over the titanium or titanium oxide such that theorientation control layer is preferentially oriented along the (100) or(001) plane. The step of forming the piezoelectric layer includes a stepof preferentially orienting the piezoelectric layer along the (001)plane by the orientation control layer.

With such features, an angular velocity sensor having the same effectsas those of the 11th invention can readily be manufactured.

The 23rd invention is directed to an ink jet recording apparatuscomprising an ink jet head, the ink jet head including: a piezoelectricelement in which a first electrode layer, an orientation control layer,a piezoelectric layer and a second electrode layer are layered in thisorder; a vibration layer provided on one surface of the piezoelectricelement that is closer to the second electrode layer; and a pressurechamber member bonded to one surface of the vibration layer that is awayfrom the piezoelectric element and including a pressure chamber forstoring ink therein, the ink jet head being capable of being relativelymoved with respect to a recording medium, in which while the ink jethead is moved with respect to the recording medium, the vibration layeris displaced in a thickness direction by a piezoelectric effect of thepiezoelectric layer of the piezoelectric element in the ink jet head soas to discharge the ink out of the pressure chamber through a nozzlehole communicated to the pressure chamber onto the recording medium,thereby recording information.

In this invention, the first electrode layer of the piezoelectricelement of the ink jet head is made of a noble metal containing titaniumor titanium oxide. The orientation control layer is made of a cubic ortetragonal perovskite oxide that is preferentially oriented along a(100) or (001) plane. The piezoelectric layer is made of a rhombohedralor tetragonal perovskite oxide that is preferentially oriented along a(001) plane. In the vicinity of one surface of the orientation controllayer that is closer to the first electrode layer, a (100)- or(001)-oriented region extends over titanium or titanium oxide located onone surface of the first electrode layer that is closer to theorientation control layer, and the cross-sectional area of the (100)- or(001)-oriented region in the direction perpendicular to the thicknessdirection gradually increases in the direction away from the firstelectrode layer toward the piezoelectric layer.

The 24th invention is directed to an ink jet recording apparatuscomprising an ink jet head, the ink jet head including: a piezoelectricelement in which a first electrode layer, an orientation control layer,a piezoelectric layer and a second electrode layer are layered in thisorder; a vibration layer provided on one surface of the piezoelectricelement that is closer to the first electrode layer; and a pressurechamber member bonded to one surface of the vibration layer that is awayfrom the piezoelectric element and including a pressure chamber forstoring ink therein, the ink jet head being capable of being relativelymoved with respect to a recording medium, in which while the ink jethead is moved with respect to the recording medium, the vibration layeris displaced in a thickness direction by a piezoelectric effect of thepiezoelectric layer of the piezoelectric element in the ink jet head soas to discharge the ink out of the pressure chamber through a nozzlehole communicated to the pressure chamber onto the recording medium,thereby recording information.

The first electrode layer of the piezoelectric element of the ink jethead is made of a noble metal containing titanium or titanium oxide. Theorientation control layer is made of a cubic or tetragonal perovskiteoxide that is preferentially oriented along a (100) or (001) plane. Thepiezoelectric layer is made of a rhombohedral or tetragonal perovskiteoxide that is preferentially oriented along a (001) plane. In thevicinity of one surface of the orientation control layer that is closerto the first electrode layer, a (100)- or (001)-oriented region extendsover titanium or titanium oxide located on one surface of the firstelectrode layer that is closer to the orientation control layer, and thecross-sectional area of the (100)- or (001)-oriented region in thedirection perpendicular to the thickness direction gradually increasesin the direction away from the first electrode layer toward thepiezoelectric layer.

With the 23rd and 24th inventions, it is possible to easily obtain anink jet recording apparatus that provides a quite desirable printingperformance and durability.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a cross-sectional view illustrating a piezoelectric elementaccording to an embodiment of the present invention.

FIG. 2 is an enlarged cross-sectional view schematically illustratingthe structure of an orientation control layer in the piezoelectricelement.

FIG. 3 is a perspective view illustrating the general structure of anink jet head according to an embodiment of the present invention.

FIG. 4 is an exploded perspective view illustrating an important part ofa pressure chamber member and an actuator section of the ink jet head.

FIG. 5 is a cross-sectional view illustrating an important part of apressure chamber member and an actuator section of the ink jet head.

FIG. 6 illustrates a deposition step, a step of forming pressure chambercavities, and an adhesive application step, respectively, in a methodfor manufacturing the ink jet head.

FIG. 7 illustrates a step of bonding a substrate after the depositionprocess and the pressure chamber member to each other, and a step offorming vertical walls, respectively, in the method for manufacturingthe ink jet head.

FIG. 8 illustrates a step of removing a substrate (for depositing filmsthereon) and an adhesive layer, and a step of dividing a first electrodelayer, respectively, in the method for manufacturing the ink jet head.

FIG. 9 illustrates a step of dividing the orientation control layer andthe piezoelectric layer, and a step of cutting off a substrate (forforming the pressure chamber member), respectively, in the method formanufacturing the ink jet head.

FIG. 10 illustrates a step of producing an ink channel member and anozzle plate, a step of bonding the ink channel member and the nozzleplate to each other, a step of bonding the pressure chamber member andthe ink channel member to each other, and a completed ink jet head,respectively, in the method for manufacturing the ink jet head.

FIG. 11 is a plan view illustrating how Si substrates on which filmshave been deposited are bonded to an Si substrate for forming thepressure chamber member in the method for manufacturing the ink jethead.

FIG. 12 is a cross-sectional view illustrating an important part of apressure chamber member and an actuator section in another ink jet headaccording to an embodiment of the present invention.

FIG. 13 illustrates a deposition step, and a step of forming a pressurechamber, respectively, in a method for manufacturing the ink jet head.

FIG. 14 is a schematic perspective view illustrating an ink jetrecording apparatus according to an embodiment of the present invention.

FIG. 15 is a schematic perspective view illustrating an angular velocitysensor according to an embodiment of the present invention.

FIG. 16 is a cross-sectional view taken along line XVI—XVI of FIG. 15.

FIG. 17 illustrates a method for manufacturing the angular velocitysensor.

FIG. 18 is a plan view illustrating the method for manufacturing theangular velocity sensor after a second electrode layer is patterned.

FIG. 19 is a schematic perspective view illustrating a conventionalangular velocity sensor using quartz.

FIG. 20 is a cross-sectional view taken along line XX—XX of FIG. 19.

BEST MODE FOR CARRYING OUT THE INVENTION EMBODIMENT 1

FIG. 1 illustrates a piezoelectric element according to an embodiment ofthe present invention. In the figure, the reference numeral 11 denotes asubstrate made of a 4-inch silicon (Si) wafer having a thickness of 0.3mm, and an adhesive layer 12 made of titanium (Ti) and having athickness of 0.02 μm is formed on the substrate 11. Note that thesubstrate 11 is not limited to an Si substrate, but may alternatively bea glass substrate, a metal substrate, a ceramic substrate, or the like.

A first electrode layer 14 having a thickness of 0.22 μm and made ofplatinum (Pt) to which 2.1 mol % of Ti is added is formed on theadhesive layer 12. The first electrode layer 14 is oriented along the(111) plane.

An orientation control layer 15 made of PLT having a cubic or tetragonalperovskite crystalline structure whose lanthanum (La) content is 12 mol% and whose lead content is 8 mol % in excess of the stoichiometriccomposition is formed on the first electrode layer 14. The orientationcontrol layer 15 is preferentially oriented along the (100) or (001)plane, and has a thickness of 0.03 μm.

A piezoelectric layer 16 having a thickness of 3 μm and made of PZThaving a rhombohedral or tetragonal perovskite crystalline structure isformed on the orientation control layer 15. The piezoelectric layer 16is preferentially oriented along the (001) plane. The Zr/Ti compositionof the PZT material is 53/47, which is near the boundary between beingtetragonal and being rhombohedral (i.e., the morphotropic phaseboundary). Note that the Zr/Ti composition of the piezoelectric layer 16is not limited to 53/47, but may be any other suitable composition aslong as it is in the range of 30/70 to 70/30. Moreover, the material ofthe piezoelectric layer 16 is not limited to any particular material, aslong as it is a piezoelectric material whose main component is PZT,e.g., those obtained by adding an additive such as Sr, Nb or Al to PZT.For example, PMN or PZN may be used. Furthermore, the thickness thereofis not limited to any particular thickness as long as it is in the rangeof 0.5 to 5.0 μm.

A second electrode layer 17 having a thickness of 0.2 μm and made of Ptis formed on the piezoelectric layer 16. Note that the material of thesecond electrode layer 17 is not limited to Pt as long as it is aconductive material, and the thickness thereof is not limited to anyparticular thickness as long as it is in the range of 0.1 to 0.4 μm.

The piezoelectric element is obtained by depositing the adhesive layer12, the first electrode layer 14, the orientation control layer 15, thepiezoelectric layer 16 and the second electrode layer 17 in this orderon the substrate 11 by a sputtering method. Note that the depositionmethod is not limited to a sputtering method, but may alternatively beany other suitable deposition method as long as a crystalline thin filmis directly formed without the crystallization step using a heattreatment (e.g., a CVD method). Moreover, the deposition method for theadhesive layer 12 and the second electrode layer 17 may be a sol-gelmethod, or the like.

The adhesive layer 12 is provided for improving the adhesion between thesubstrate 11 and the first electrode layer 14. The material of theadhesive layer 12 is not limited to Ti, but may alternatively betantalum, iron, cobalt, nickel, chromium, or a compound thereof(including Ti). Moreover, the thickness thereof is not limited to anyparticular thickness as long as it is in the range of 0.005 to 1 μm. Theadhesive layer 12 is not always necessary. Even if the first electrodelayer 14 is formed directly on the substrate 11, the adhesion betweenthe substrate 11 and the first electrode layer 14 is quite desirablebecause Ti is contained in the first electrode layer 14.

The first electrode layer 14 not only functions as an electrode, butalso functions, with the addition of Ti, to preferentially orient theorientation control layer 15 along the (100) or (001) plane. Titaniumoxide may be added in place of Ti. The amount of titanium or titaniumoxide to be added is preferably greater than zero and less than or equalto 30 mol %. Moreover, the material of the first electrode layer 14 maybe at least one noble metal selected from the group consisting of Pt,iridium, palladium and ruthenium, and the thickness thereof is notlimited to any particular thickness as long as it is in the range of0.05 to 2 μm. Titanium or titanium oxide existing at a surface of thefirst electrode layer 14 that is closer to the orientation control layer15 is intended to be contained in the first electrode layer 14, but isnot intended to be provided above the surface of the first electrodelayer 14. Thus, the titanium or titanium oxide hardly protrudes abovethe surface of the first electrode layer 14 that is closer to theorientation control layer 15. Even if it protrudes, the amount ofprotrusion is smaller than 2 nm.

The orientation control layer 15 is provided for improving thecrystallinity and the (001) orientation property of the piezoelectriclayer 16. For this purpose, the orientation control layer 15 is made ofPLT, which contains La and contains no Zr and whose lead content is inexcess of the stoichiometric composition. Note that in order to improvethe crystallinity and the orientation of the piezoelectric layer 16, theLa content thereof may be greater than zero and less than or equal to 25mol %, and the lead content thereof may be in excess of thestoichiometric composition by an amount greater than zero and less thanor equal to 30 mol %. Moreover, the material of the orientation controllayer 15 is not limited to PLT as described above, but may alternativelybe PLZT obtained by adding zirconium to PLT, or may be a materialobtained by adding at least one of magnesium and manganese to PLT orPLZT. The zirconium content is preferably less than or equal to 20 mol%, and when at least one of magnesium and manganese is added, the totalamount thereof to be added is preferably greater than zero and less thanor equal to 10 mol % (the amount of one of magnesium and manganese maybe zero). The thickness of the orientation control layer 15 is notlimited to any particular thickness as long as it is in the range of0.01 to 0.2 μm.

In the vicinity of one surface of the orientation control layer 15 thatis closer to the first electrode layer 14, a (100)- or (001)-orientedregion 15 a extends over titanium (exactly speaking, this is titaniumoxide in the case where titanium oxide is contained in the firstelectrode layer 14, but even in the case where titanium is contained inthe first electrode layer 14, this may sometimes be titanium oxidebecause of oxidation) located on one surface of the first electrodelayer 14 that is closer to the orientation control layer 15, asillustrated in FIG. 2, so that the cross-sectional area of the region 15a in the direction perpendicular to the thickness direction graduallyincreases in the direction away from the first electrode layer 14 towardthe piezoelectric layer 16. On the other hand, since the first electrodelayer 14 is oriented along the (111) plane, each region 15 b of theorientation control layer 15, which is located over a portion of thesurface of the first electrode layer 14 where none of titanium andtitanium oxide exist, is not oriented along the (100) or (001) plane,but is oriented along the (111) plane in the present embodiment (theregion 15 b may be oriented in a direction other than along the (111)plane or may be amorphous depending on the material of the firstelectrode layer 14). Such a region 15 b that is not oriented along the(100) or (001) plane extends only within a distance of about 20 nm atmaximum from the surface of the orientation control layer 15 that iscloser to the first electrode layer 14. If the thickness of theorientation control layer 15 is 0.02 μm or more, the (100)- or(001)-oriented region 15 a extends substantially across the entiresurface of the orientation control layer 15 that is closer to thepiezoelectric layer 16.

The piezoelectric layer 16 is preferentially oriented along the (001)plane by the orientation control layer 15, and the degree of (001)orientation, α, of the piezoelectric layer 16 is 90% or more.

Note that it is not necessary that the region 15 a extends substantiallyacross the entire surface of the orientation control layer 15 that iscloser to the piezoelectric layer 16. The region 15 b that is notoriented along the (100) or (001) plane may partially exist on thatsurface due to the fairly small thickness of the orientation controllayer 15. However, even in such a case, if the thickness of theorientation control layer 15 is 0.01 μm or more, a (100)- or(001)-oriented region extends across a major portion of the surface ofthe orientation control layer 15 that is closer to the piezoelectriclayer 16, with the degree of (001) orientation of the piezoelectriclayer 16 being as high as 90% or more.

Next, a method for manufacturing a piezoelectric element as describedabove will be described.

The adhesive layer 12, the first electrode layer 14, the orientationcontrol layer 15, the piezoelectric layer 16 and the second electrodelayer 17 are deposited in this order on the Si substrate 11 by asputtering method.

The adhesive layer 12 is obtained by using a Ti target and applying ahigh-frequency power of 100 W thereto for 1 minute while heating thesubstrate 11 to 400° C. in an argon gas at 1 Pa.

The first electrode layer 14 is obtained by using a Ti target and a Pttarget and applying high-frequency powers of 85 W and 200 W thereto for12 minutes while heating the substrate 11 to 400° C. in an argon gas at1 Pa, using a multi-target sputtering apparatus. Titanium exists in adotted pattern on one surface of the obtained first electrode layer 14that is away from the adhesive layer 12.

The gas used for forming the first electrode layer 14 by the sputteringmethod may be only an argon gas as described above, or may be a mixedgas of argon and oxygen. In the case where the argon gas is solely used,titanium on the surfaces of the first electrode layer 14 is notoxidized. In the case where the mixed gas of argon and oxygen is used,the titanium is oxidized to become titanium oxide. In the case where themixed gas of argon and oxygen is used, the temperature of the substrate11 is desirably set to 650° C. or lower. This is because, if thetemperature of the substrate 11 is higher than 650° C., not onlytitanium but also the surface of a noble metal is slightly oxidized, andaccordingly, the crystallinity and the orientation of the orientationcontrol layer 15 formed above the substrate 11 may be adverselyinfluenced.

The orientation control layer 15 is obtained by using a sinter targetprepared by adding a 12 mol % excess of lead oxide (PbO) to PLTcontaining 14 mol % of lanthanum and applying a high-frequency power of300 W thereto for 12 minutes while heating the substrate 11 to 600° C.in a mixed atmosphere of argon and oxygen (gas volume ratio: Ar:O₂=19:1)at a degree of vacuum of 0.8 Pa.

The oxygen partial pressure in the mixed gas of argon and oxygen whichis used for forming the orientation control layer 15 by the sputteringmethod is preferably greater than 0% and less than or equal to 10%. Thisis because the crystallinity of the orientation control layer 15deteriorates in an environment where no oxygen exists. If the oxygenpartial pressure is higher than 10%, the orientation of the (100) or(001) plane deteriorates. Further, the degree of vacuum is preferably0.05 Pa or higher and 5 Pa or lower. This is because, if the degree ofvacuum is lower than 0.05 Pa, the crystallinity of the orientationcontrol layer 15 becomes non-uniform. If the degree of vacuum is higherthan 5 Pa, the orientation of the (100) or (001) plane deteriorates.

When forming the orientation control layer 15 by the sputtering method,the temperature of the substrate 11 is desirably set to 450° C. orhigher and 750° C. or lower. This is because, if the temperature of thesubstrate 11 is lower than 450° C., the crystallinity of the orientationcontrol layer 15 deteriorates, and pyrochlore is more likely to begenerated. If the temperature of the substrate 11 is 750° C. or higher,Pb contained in the film of the orientation control layer 15 evaporatesduring the formation of the film, so that the orientation control layer15 lacks Pb. As a result, the crystallinity of the orientation controllayer 15 deteriorates.

More preferably, the oxygen partial pressure is set to 0.5% or higherand 10% or lower, the degree of vacuum is set to 0.1 Pa or higher and 2Pa or lower, and the temperature of the substrate 11 is 500° C. orhigher and 650° C. or lower.

In the case of forming the orientation control layer 15 according to theabove conditions, the orientation control layer 15 grows using titanium,which exists in a dotted pattern on one surface of the first electrodelayer 14 that is closer to the orientation control layer 15, as anucleus, whereby the orientation control layer 15 is likely to beoriented along the (100) or (001) plane over titanium. Since, asdescribed above, the titanium hardly protrudes above the surface of thefirst electrode layer 14 (even if it protrudes, the amount of protrusionis smaller than 2 nm), the orientation control layer 15 is more likelyto be oriented along the (100) or (001) plane. On the other hand, sincethe first electrode layer 14 is oriented along the (111) plane, regionsof the orientation control layer 15 located over portions of the surfaceof the first electrode layer 14 where titanium does not exist are notoriented along the (100) or (001) plane (but is oriented along the (111)plane in the present embodiment). As the crystal growth processproceeds, these regions gradually shrink while the (100)- or(001)-oriented region gradually expands. As a result, in the vicinity ofthe first electrode layer 14, the orientation control layer 15 has the(100)- or (001)-oriented region 15 a (over titanium located on onesurface of the first electrode layer 14 that is closer to theorientation control layer 15) and the region 15 b that is not orientedalong the (100) or (001) plane (over portions of the surface of thefirst electrode layer 14 where titanium does not exist), as describedabove. The cross-sectional area of the (100)- or (001)-oriented region15 a increases in the direction away from the first electrode layer 14toward the other side (i.e., toward the piezoelectric layer 16). At thesurface of the orientation control layer 15 that is closer to thepiezoelectric layer 16, the (100)- or (001)-oriented region 15 a extendssubstantially across the entire surface of the orientation control layer15. In the case where the zirconium content is set to 20 mol % or less,and the lanthanum content is set to greater than 0 and less than orequal to 25 mol %, the crystallinity and the orientation of theorientation control layer 15 are significantly improved. Especially asthe zirconium content decreases, a layer of a low crystallinity made ofa Zr oxide is less likely to be formed in the initial period of thecrystal growth process. As a result, deterioration in the crystallinityis surely suppressed.

The piezoelectric layer 16 is obtained by using a sinter target of PZT(Zr/Ti=53/47) and applying a high-frequency power of 250 W thereto for 3hours while heating the substrate 11 to 610° C. in a mixed atmosphere ofargon and oxygen (gas volume ratio: Ar:O₂=19:1) at a degree of vacuum of0.3 Pa.

The oxygen partial pressure in the mixed gas of argon and oxygen whichis set for forming the piezoelectric layer 16 by the sputtering methodis preferably greater than 0% and less than or equal to 30%. This isbecause the crystallinity of the piezoelectric layer 16 deteriorates inan environment where no oxygen exists. If the oxygen partial pressure ishigher than 30%, the orientation of the (001) plane deteriorates.Further, the degree of vacuum is preferably 0.1 Pa or higher and 1 Pa orlower. This is because, if the degree of vacuum is lower than 0.1 Pa,the crystallinity and the piezoelectric characteristics of thepiezoelectric layer 16 become non-uniform. If the degree of vacuum ishigher than 1 Pa, the orientation of the (001) plane deteriorates.

The temperature of the substrate 11 which is selected for forming thepiezoelectric layer 16 by the sputtering method is preferably 450° C. orhigher and 750° C. or lower. This is because, if the temperature of thesubstrate 11 is lower than 450° C., the crystallinity of thepiezoelectric layer 16 deteriorates, and pyrochlore is more likely to begenerated. If the temperature of the substrate 11 is higher than 750°C., Pb contained in the film of the piezoelectric layer 16 evaporatesduring the formation of the film, so that the piezoelectric layer 16lacks Pb. As a result, the crystallinity of the piezoelectric layer 16deteriorates.

More preferably, the oxygen partial pressure is set to 1% or higher and10% or lower, the degree of vacuum is set to 0.15 Pa or higher and 0.8Pa or lower, and the temperature of the substrate 11 is 525° C. orhigher and 625° C. or lower.

In the case of forming the piezoelectric layer 16 according to the aboveconditions, since the surface of the orientation control layer 15 thatis closer to the piezoelectric layer 16 is oriented along the (100) or(001) plane, the piezoelectric layer 16 is oriented along the (001)plane (herein Zr/Ti=53/47, and thus the crystal is rhombohedral; sincethe (100) plane and the (001) plane are the same in a rhombohedralsystem, the rhombohedral (100) orientation is included herein), wherebythe degree of (001) orientation thereof (the degree of (100) orientationof the rhombohedral system) is 90% or more. Moreover, since theorientation control layer 15 has a desirable crystallinity, thepiezoelectric layer 16 also has a desirable crystallinity.

The second electrode layer 17 is obtained by using a Pt target andapplying a high-frequency power of 200 W thereto for 10 minutes at aroom temperature in an argon gas at 1 Pa.

Thus, in the piezoelectric element of the present embodiment, thepiezoelectric layer 16 having a desirable crystallinity and a desirableorientation can be obtained by depositing it by a sputtering method onthe inexpensive silicon substrate 11, without using an expensive MgOsingle-crystal substrate. Therefore, it is possible to suppress thedeviation in the piezoelectric characteristics of the piezoelectricelement and to improve the reliability thereof while reducing themanufacturing cost. Moreover, a layer of a low crystallinity made of aZr oxide is less likely to be formed, whereby it is possible to increasethe breakdown voltage of the piezoelectric element.

Next, specific examples of the present invention will be described. Ineach of Examples 1–5, a structure in which an adhesive layer, a firstelectrode layer, an orientation control layer, a piezoelectric layer,and a second electrode layer are formed on a substrate in this order(except that an adhesive layer is not formed in Example 5) is the sameas that described in the above embodiment.

EXAMPLE 1

A piezoelectric element of Example 1 was produced by using the samematerial, thickness and manufacturing method for each film as those ofthe embodiment described above. No crack or peeling off was observed forany of the films of the piezoelectric element of Example 1.

The crystal orientation and the film composition of the piezoelectriclayer before the formation of the second electrode layer were examined.Specifically, an analysis by an X-ray diffraction method showed that thepiezoelectric layer had a (100)-oriented rhombohedral perovskitecrystalline structure (degree of (100) orientation: α=97%). Moreover, ananalysis of the composition of the PZT film with an X-ray microanalyzershowed that the Zr/Ti ratio was 53/47 as in the target composition.

Then, the crystal orientation and the film composition of the firstelectrode layer before the formation of the orientation control layerwere examined. Specifically, an analysis by an X-ray diffraction methodshowed that the Pt film was oriented along the (111) plane. Moreover, ananalysis of the composition at a depth of 5 nm from the surface withX-ray photoelectron spectroscopy (XPS) showed that the Ti content was2.1 mol %.

Then, the crystal orientation and the film composition of theorientation control layer before the formation of the piezoelectriclayer were examined. The PLT film of the orientation control layer had a(100)-oriented perovskite crystalline structure. Note that a(111)-oriented region was observed on one side of the orientationcontrol layer that is closer to the first electrode layer. It isbelieved that the (111)-oriented region exists over a portion of thesurface of the first electrode layer where titanium does not exist.Moreover, a composition analysis with an X-ray microanalyzer showed that12 mol % of lanthanum was contained, and an 8 mol % excess of Pb wascontained.

Next, before the formation of the second electrode layer, 100cantilevers having a size of 15 mm×2 mm were cut out by dicing. Then,the second electrode layer having a thickness of 0.2 μm was formedthereon by a sputtering method, and the piezoelectric constant d31 wasmeasured (see, for example, Japanese Unexamined Patent Publication No.2001-21052 for the method for measuring the piezoelectric constant d31).The average piezoelectric constant of the 100 cantilevers was −127 pC/N(deviation: σ4.2%).

Then, the second electrode layer of the piezoelectric element was formedas 65 pieces of Pt film each having a size of 1 mm×1 mm and a thicknessof 0.2 nm and arranged at an interval of 10 mm by a sputtering methodusing a metal mask. The breakdown voltage was measured by applying avoltage between each second electrode layer and the first electrodelayer. Note that the breakdown voltage value was defined to be the valueof the applied voltage for which the current value was 1 μA. As aresult, the average breakdown voltage value was 118 V (deviation:σ=4.2%).

EXAMPLE 2

In Example 2, a 4-inch stainless steel (SUS304) having a thickness of0.25 mm was used as the substrate, a tantalum (Ta) film having athickness of 0.01 μm was used as the adhesive layer, a Pt film having athickness of 0.25 μm and containing 8 mol % of titanium oxide was usedas the first electrode layer, a PLT film (to which 3 mol % of magnesiumwas added) having a thickness of 0.03 μm and containing 17 mol % oflanthanum in which the lead content was 6 mol % in excess of thestoichiometric composition was used as the orientation control layer, aPZT film (Zr/Ti=40/60) having a thickness of 2.7 μm was used as thepiezoelectric layer, and a Pt film having a thickness of 0.1 μm was usedas the second electrode layer.

The adhesive layer was obtained by using a Ta target and applying ahigh-frequency power of 100 W thereto for 1 minute while heating thesubstrate to 500° C. in an argon gas at 1 Pa.

The first electrode layer was obtained by using a Ti target and a Pttarget and applying high-frequency powers of 120 W and 200 W thereto,respectively, for 12 minutes while heating the substrate to 400° C. in amixed atmosphere of argon and oxygen at 1 Pa (gas volume ratio:Ar:O₂=15:1), using a multi-target sputtering apparatus.

The orientation control layer was obtained by using a sinter target,which was prepared by adding 3 mol % of magnesium and a 10 mol % excessof lead oxide (PbO) to PLT containing 20 mol % of lanthanum, andapplying a high-frequency power of 300 W thereto for 15 minutes at asubstrate temperature of 600° C. in a mixed atmosphere of argon andoxygen (gas volume ratio: Ar:O₂=19:1) at a degree of vacuum of 0.8 Pa.

The piezoelectric layer was obtained by using a sinter target of PZT(Zr/Ti=40/60) and applying a high-frequency power of 250 W thereto for 3hours at a substrate temperature of 600° C. in a mixed atmosphere ofargon and oxygen (gas volume ratio: Ar:O₂=19:1) at a degree of vacuum of0.3 Pa.

The second electrode layer was obtained by using a Pt target andapplying a high-frequency power of 200 W thereto at a room temperaturein an argon gas at 1 Pa.

Also in Example 2, no crack or peeling off was observed for any of thefilms of the piezoelectric element.

Then, the crystal orientation and the film composition of thepiezoelectric layer before the formation of the second electrode layerwere examined as in Example 1, indicating that the piezoelectric layerhad a (001)-oriented tetragonal perovskite crystalline structure (degreeof (001) orientation: α=98%). Moreover, an examination of thecomposition of the PZT film showed that the Zr/Ti ratio was 40/60 as inthe target composition.

Then, the crystal orientation and the film composition of the firstelectrode layer before the formation of the orientation control layerwere examined, indicating that the Pt film was oriented along the (111)plane. Moreover, the titanium oxide content was 8 mol %.

Then, the crystal orientation and the film composition of theorientation control layer before the formation of the piezoelectriclayer were examined, indicating that the PLT film had a (001)-orientedperovskite crystalline structure. Note that a (111)-oriented region wasobserved on one side of the orientation control layer that is closer tothe first electrode layer. It is believed that the (111)-oriented regionexists over a portion of the surface of the first electrode layer wheretitanium oxide does not exist. Moreover, 3 mol % of magnesium and 17 mol% of lanthanum were contained, and a 6 mol % excess of Pb was contained.

Next, as in Example 1, before the formation of the second electrodelayer, 100 cantilevers having a size of 15 mm×2 mm were cut out bydicing. Then, the second electrode layer having a thickness of 0.1 μmwas formed thereon by a sputtering method, and the piezoelectricconstant d31 was measured. The average piezoelectric constant of the 100cantilevers was −129 pC/N (deviation: σ=2.9%).

Then, the second electrode layer of the piezoelectric element was formedas 65 pieces of Pt film each having a size of 1 mm×1 mm and a thicknessof 0.1 μm and arranged at an interval of 10 mm by a sputtering methodusing a metal mask. The breakdown voltage was measured by applying avoltage between each second electrode layer and the first electrodelayer. As a result, the average breakdown voltage value was 118 V(deviation: σ=4.8%).

EXAMPLE 3

In Example 3, a barium borosilicate glass having a thickness of 0.5 mm(size: 100 mm×100 mm) was used as the substrate, a nickel (Ni) filmhaving a thickness of 0.005 μm was used as the adhesive layer, aniridium (Ir) film having a thickness of 0.15 μm and containing 18 mol %of titanium was used as the first electrode layer, a PLT film (to which1 mol % of manganese was added) having a thickness of 0.02 μm andcontaining 8 mol % of lanthanum in which the lead content was 16 mol %in excess of the stoichiometric composition was used as the orientationcontrol layer, a PZT film (Zr/Ti=60/40) having a thickness of 2.6 μm wasused as the piezoelectric layer, and a Pt film having a thickness of0.01 μm was used as the second electrode layer.

The adhesive layer was obtained by using an Ni target and applying ahigh-frequency power of 200 W thereto for 1 minute while heating thesubstrate to 300° C. in an argon gas at 1 Pa.

The first electrode layer was obtained by using a Ti target and an Irtarget and applying high-frequency powers of 160 W and 200 W thereto,respectively, for 10 minutes while heating the substrate to 600° C. inan argon gas at 1 Pa, using a multi-target sputtering apparatus.

The orientation control layer was obtained by using a sinter target,which was prepared by adding 2 mol % of manganese and a 22 mol % excessof lead oxide (PbO) to PLT containing 12 mol % of lanthanum, andapplying a high-frequency power of 300 W thereto for 15 minutes at asubstrate temperature of 580° C. in a mixed atmosphere of argon andoxygen (gas volume ratio: Ar:O₂=19:1) at a degree of vacuum of 0.8 Pa.

The piezoelectric layer was obtained by using a sinter target of PZT(Zr/Ti=60/40) and applying a high-frequency power of 260 W thereto for 3hours at a substrate temperature of 580° C. in a mixed atmosphere ofargon and oxygen (gas volume ratio: Ar:O₂=19:1) at a degree of vacuum of0.3 Pa.

The second electrode layer was obtained by using a Pt target andapplying a high-frequency power of 200 W thereto at a room temperaturein an argon gas at 1 Pa.

Also in Example 3, no crack or peeling off was observed for any of thefilms of the piezoelectric element.

Then, the crystal orientation and the film composition of thepiezoelectric layer before the formation of the second electrode layerwere examined, indicating that the piezoelectric layer had a(100)-oriented rhombohedral perovskite crystalline structure (degree of(100) orientation: α=95%). Moreover, an examination of the compositionof the PZT film showed that the Zr/Ti ratio was 60/40 as in the targetcomposition.

Then, the crystal orientation and the film composition of the firstelectrode layer before the formation of the orientation control layerwere examined, indicating that the Ir film was oriented along the (111)plane. Moreover, the Ti content was 18 mol %.

Then, the crystal orientation and the film composition of theorientation control layer before the formation of the piezoelectriclayer were examined, indicating that the PLT film had a (100)-orientedperovskite crystalline structure. Note that an amorphous region wasobserved on one side of the orientation control layer that is closer tothe first electrode layer. It is believed that the amorphous regionexists over a portion of the surface of the first electrode layer wheretitanium does not exist. Moreover, 1 mol % of manganese and 8 mol % oflanthanum were contained, and a 16 mol % excess of Pb was contained.

Next, before the formation of the second electrode layer, 100cantilevers having a size of 15 mm×2 mm were cut out by dicing. Then,the second electrode layer having a thickness of 0.01 μm was formedthereon by a sputtering method, and the piezoelectric constant d31 wasmeasured. The average piezoelectric constant of the 100 cantilevers was−122 pC/N (deviation: σ=3.6%).

Then, the second electrode layer of the piezoelectric element was formedas 65 pieces of Pt film each having a size of 1 mm×1 mm and a thicknessof 0.01 μm and arranged at an interval of 10 mm by a sputtering methodusing a metal mask. The breakdown voltage was measured by applying avoltage between each second electrode layer and the first electrodelayer. As a result, the average breakdown voltage value was 115 V(deviation: σ=5.2%).

EXAMPLE 4

In Example 4, a 4-inch silicon wafer having a thickness of 0.5 mm wasused as the substrate, a titanium film having a thickness of 0.01 μm wasused as the adhesive layer, an Ir film having a thickness of 0.25 μm andcontaining 5 mol % of titanium oxide was used as the first electrodelayer, a PLT film having a thickness of 0.05 μm and containing 10 mol %of lanthanum in which the lead content was 10 mol % in excess of thestoichiometric composition was used as the orientation control layer, aPZT film (Zr/Ti=52/48) having a thickness of 3.2 μm was used as thepiezoelectric layer, and a Pt film having a thickness of 0.01 μm wasused as the second electrode layer.

The adhesive layer was obtained by using an Ti target and applying ahigh-frequency power of 100 W thereto for 1 minute while heating thesubstrate to 500° C. in an argon gas at 1 Pa.

The first electrode layer was obtained by using a Ti target and an Irtarget and applying high-frequency powers of 90 W and 200 W thereto,respectively, for 12 minutes while heating the substrate to 400° C. in amixed atmosphere of argon and oxygen (gas volume ratio: Ar:O₂=10:1) at 1Pa, using a multi-target sputtering apparatus.

The orientation control layer was obtained by using a sinter targetprepared by adding a 14 mol % excess of lead oxide (PbO) to PLTcontaining 10 mol % of lanthanum and applying a high-frequency power of300 W thereto for 20 minutes at a substrate temperature of 600° C. in amixed atmosphere of argon and oxygen (gas volume ratio: Ar:O₂=15:1) at adegree of vacuum of 0.84 Pa.

The piezoelectric layer was obtained by using a sinter target of PZT(Zr/Ti=52/48) and applying a high-frequency power of 270 W thereto for 3hours at a substrate temperature of 620° C. in a mixed atmosphere ofargon and oxygen (gas volume ratio: Ar:O₂=19:1) at a degree of vacuum of0.4 Pa.

The second electrode layer was obtained by using a Pt target andapplying a high-frequency power of 200 W thereto at a room temperaturein an argon gas at 1 Pa.

Also in Example 4, no crack or peeling off was observed for any of thefilms of the piezoelectric element.

Then, the crystal orientation and the film composition of thepiezoelectric layer before the formation of the second electrode layerwere examined, indicating that the piezoelectric layer had a(100)-oriented rhombohedral perovskite crystalline structure (degree of(100) orientation: α=99%). Moreover, an examination of the compositionof the PZT film showed that the Zr/Ti ratio was 52/48 as in the targetcomposition.

Then, the crystal orientation and the film composition of the firstelectrode layer before the formation of the orientation control layerwere examined, indicating that the Ir film was oriented along the (111)plane. Moreover, the titanium oxide content was 5 mol %.

Then, the crystal orientation and the film composition of theorientation control layer before the formation of the piezoelectriclayer were examined, indicating that the PLT film had a (100)-orientedperovskite crystalline structure. Note that an amorphous region wasobserved on one side of the orientation control layer that is closer tothe first electrode layer. It is believed that the amorphous regionexists over a portion of the surface of the first electrode layer wheretitanium oxide does not exist. Moreover, 10 mol % of lanthanum wascontained, and a 10 mol % excess of Pb was contained.

Next, before the formation of the second electrode layer, 100cantilevers having a size of 15 mm×2 mm were cut out by dicing. Then,the second electrode layer having a thickness of 0.01 μm was formedthereon by a sputtering method, and the piezoelectric constant d31 wasmeasured. The average piezoelectric constant of the 100 cantilevers was−141 pC/N (deviation: σ=2.4%).

Then, the second electrode layer of the piezoelectric element was formedas 65 pieces of Pt film each having a size of 1 mm×1 mm and a thicknessof 0.01 μm and arranged at an interval of 10 mm by a sputtering methodusing a metal mask. The breakdown voltage was measured by applying avoltage between each second electrode layer and the first electrodelayer. As a result, the average breakdown voltage value was 122 V(deviation: σ=4.1%).

EXAMPLE 5

In Example 5, a 4-inch silicon wafer having a thickness of 0.3 mm wasused as the substrate, the first electrode layer was formed directly onthe substrate without providing the adhesive layer therebetween, a Ptfilm having a thickness of 0.22 μm and containing 2.1 mol % of titaniumwas used as the first electrode layer, a PLZT film (to which 3 mol % ofmagnesium was added) having a thickness of 0.03 μm and containing 12 mol% of lanthanum and 15 mol % of zirconium in which the lead content was18 mol % in excess of the stoichiometric composition was used as theorientation control layer, a PZT film (Zr/Ti=53/47) having a thicknessof 3 μm was used as the piezoelectric layer, and a Pt film having athickness of 0.2 μm was used as the second electrode layer.

The first electrode layer was obtained by using a Ti target and a Pttarget and applying high-frequency powers of 85 W and 200 W thereto,respectively, for 12 minutes while heating the substrate to 400° C. inan argon gas at 1 Pa, using a multi-target sputtering apparatus.

The orientation control layer was obtained by using a sinter target,which was prepared by adding 3 mol % of magnesium and a 24 mol % excessof lead oxide (PbO) to PLZT containing 14 mol % of lanthanum and 15 mol% of zirconium, and applying a high-frequency power of 300 W thereto for12 minutes at a substrate temperature of 600° C. in a mixed atmosphereof argon and oxygen (gas volume ratio: Ar:O₂=19:1) at a degree of vacuumof 0.8 Pa.

The piezoelectric layer was obtained by using a sinter target of PZT(Zr/Ti=53/47) and applying a high-frequency power of 250 W thereto for 3hours at a substrate temperature of 610° C. in a mixed atmosphere ofargon and oxygen (gas volume ratio: Ar:O₂=19:1) at a degree of vacuum of0.3 Pa.

The second electrode layer was obtained by using a Pt target andapplying a high-frequency power of 200 W thereto at a room temperaturein an argon gas at 1 Pa.

Also in Example 5, no crack or peeling off was observed for any of thefilms of the piezoelectric element.

Then, the crystal orientation and the film composition of thepiezoelectric layer before the formation of the second electrode layerwere examined, indicating that the piezoelectric layer had a(100)-oriented rhombohedral perovskite crystalline structure (degree of(100) orientation: α=98%). Moreover, an examination of the compositionof the PZT film showed that the Zr/Ti ratio was 53/47 as in the targetcomposition.

Then, the crystal orientation and the film composition of the firstelectrode layer before the formation of the orientation control layerwere examined, indicating that the Pt film was oriented along the (111)plane. Moreover, the titanium content was 2.1 mol %.

Then, the crystal orientation and the film composition of theorientation control layer before the formation of the piezoelectriclayer were examined, indicating that the PLT film had a (100)-orientedperovskite crystalline structure. Note that a (111)-oriented region wasobserved on one side of the orientation control layer that is closer tothe first electrode layer. It is believed that the (111)-oriented regionexists over a portion of the surface of the first electrode layer wheretitanium does not exist. Moreover, 3 mol % of magnesium and 12 mol % oflanthanum were contained, and a 18 mol % excess of Pb was contained.

Next, before the formation of the second electrode layer, 100cantilevers having a size of 15 mm×2 mm were cut out by dicing. Then,the second electrode layer having a thickness of 0.2 μm was formedthereon by a sputtering method, and the piezoelectric constant d31 wasmeasured. The average piezoelectric constant of the 100 cantilevers was−130 pC/N (deviation: σ=4.12%).

Then, the second electrode layer of the piezoelectric element was formedas 65 pieces of Pt film each having a size of 1 mm×1 mm and a thicknessof 0.2 μm and arranged at an interval of 10 mm by a sputtering methodusing a metal mask. The breakdown voltage was measured by applying avoltage between each second electrode layer and the first electrodelayer. As a result, the average breakdown voltage value was 120 V(deviation: σ=4.0%).

COMPARATIVE EXAMPLE

A piezoelectric element of Comparative Example is different from that ofExample 1 only in that an orientation control layer is not provided. Inthe piezoelectric element of Comparative Example, an adhesive layer, afirst electrode layer, a piezoelectric layer, and a second electrodelayer are formed on a substrate in this order.

The piezoelectric layer of the piezoelectric element of ComparativeExample had a (100)-oriented rhombohedral perovskite crystallinestructure (degree of (100) orientation: α=31%).

Moreover, the piezoelectric constant d31 was measured as in Example 1,indicating that the average piezoelectric constant was −72 pC/N(deviation: σ=11.5%).

Furthermore, the breakdown voltage was measured as in Example 1,indicating that the average breakdown voltage value was 65 V (deviation:σ=14.5%).

It is thus understood that, only by providing the orientation controllayer as in Example 1, it is possible to improve the crystallinity andthe orientation of the piezoelectric layer, and to improve thepiezoelectric characteristics and the breakdown voltage of thepiezoelectric element.

EXAMPLE 6

A piezoelectric element of Example 6 is different from that of Example 1only in the material of the orientation control layer. (Note that thesputtering conditions for the orientation control layer of Example 6 arethe same as those employed in Example 1.) Specifically, the orientationcontrol layer of Example 6 is made of lead titanate (PT) not containingLa. The lead content of the orientation control layer is not in excessof the stoichiometric composition.

The piezoelectric layer of the piezoelectric element of Example 6 had a(100)-oriented rhombohedral perovskite crystalline structure (degree of(100) orientation: α=41%). Moreover, the average piezoelectric constantwas −82 pC/N (deviation: σ=9.2%). Furthermore, the average breakdownvoltage value was 82 V (deviation: σ=12.1%).

It is thus understood that, even with such an orientation control layerof Example 6, it is possible to improve the crystallinity and theorientation of the piezoelectric layer and to improve the piezoelectriccharacteristics and the breakdown voltage of the piezoelectric elementas compared with the piezoelectric element of Comparative Example.

Furthermore, as seen from the comparison with Example 1, by addinglanthanum to the orientation control layer and excessively providing Pb,the orientation of the piezoelectric layer is significantly improved.

EMBODIMENT 2

FIG. 3 illustrates the general structure of an ink jet head according toan embodiment of the present invention, and FIG. 4 illustrates thestructure of an important part thereof. In FIG. 3 and FIG. 4, thereference character A denotes a pressure chamber member. A pressurechamber cavity 101 is formed running through the pressure chamber memberA in the thickness direction (vertical direction) thereof. The referencecharacter B denotes an actuator section placed so as to cover the upperopening of the pressure chamber cavity 101, and the reference characterC denotes an ink channel member placed so as to cover the lower openingof the pressure chamber cavity 101. Each pressure chamber cavity 101 ofthe pressure chamber member A is closed by the actuator section B andthe ink channel member C, placed on and under the pressure chambermember A, respectively, thereby forming a pressure chamber 102.

The actuator section B includes a first electrode layer 103 (separateelectrode) above each pressure chamber 102. The position of the firstelectrode layer 103 generally corresponds to that of the pressurechamber 102. As can be seen from FIG. 3, a large number of pressurechambers 102 and first electrode layers 103 are arranged in a staggeredpattern.

The ink channel member C includes a common ink chamber 105 shared by anumber of pressure chambers 102 arranged in the ink supply direction, asupply port 106 through which ink in the common ink chamber 105 issupplied into the pressure chamber 102, and an ink channel 107 throughwhich ink in the pressure chamber 102 is discharged.

The reference character D denotes a nozzle plate. The nozzle plate Dincludes nozzle holes 108 each of which is communicated to the inkchannel 107. Moreover, the reference character E denotes an IC chip. Avoltage is supplied from the IC chip E to each separate electrode 103via a bonding wire BW.

Next, the structure of the actuator section B will be described withreference to FIG. 5. FIG. 5 is a cross-sectional view taken along thedirection perpendicular to the ink supply direction shown in FIG. 3. Forthe purpose of illustration, FIG. 5 shows the pressure chamber member Aincluding four pressure chambers 102 arranged in the directionperpendicular to the ink supply direction. The actuator section Bincludes: the first electrode layers 103 each located above one pressurechamber 102 so that the position of the first electrode layer 103generally corresponds to that of the pressure chamber 102, anorientation control layer 104 provided on (under, as shown in thefigure) each first electrode layer 103, a piezoelectric layer 110provided on (under) the orientation control layer 104, a secondelectrode layer 112 (common electrode) provided on (under) thepiezoelectric layers 110 and shared by all the piezoelectric layers 110,a vibration layer 111 provided on (under) the second electrode layer112, which is displaced and vibrates in the thickness direction by thepiezoelectric effect of the piezoelectric layer 110, and an intermediatelayer 113 (vertical wall) provided on (under) the vibration layer 111and located above a partition wall 102 a for partitioning the pressurechambers 102 from one another. The first electrode layer 103, theorientation control layer 104, the piezoelectric layer 110 and thesecond electrode layer 112 are arranged in this order to form apiezoelectric element. Moreover, the vibration layer 111 is provided onone surface of the piezoelectric element that is closer to the secondelectrode layer 112.

Note that in FIG. 5, the reference numeral 114 denotes an adhesive forbonding the pressure chamber member A and the actuator section B to eachother. Therefore, even if a portion of the adhesive 114 runs out of thepartition wall 102 a in the adhesion process using the adhesive 114, theintermediate layer 113 functions to increase the distance between theupper surface of the pressure chamber 102 and the lower surface of thevibration layer 111 so that such a portion of the adhesive 114 does notattach to the vibration layer 111 and that the vibration layer 111 willbe displaced and vibrate as intended. Thus, it is preferred that thepressure chamber member A is bonded to one surface of the vibrationlayer 111 of the actuator section B that is away from the secondelectrode layer 112 via the intermediate layer 113 therebetween.However, the pressure chamber member A may alternatively be bondeddirectly to one surface of the vibration layer 111 that is away from thesecond electrode layer 112.

The materials of the first electrode layer 103, the orientation controllayer 104, the piezoelectric layer 110 and the second electrode layer112 are similar to those of the first electrode layer 14, theorientation control layer 15, the piezoelectric layer 16 and the secondelectrode layer 17, respectively, of Embodiment 1. (The contents ofconstituent elements may differ.) Moreover, the structures of theorientation control layer 104 and the piezoelectric layer 110 aresimilar to those of the orientation control layer 15 and thepiezoelectric layer 16, respectively. In the vicinity of one surface ofthe orientation control layer 104 that is closer to the first electrodelayer 103, a (100)- or (001)-oriented region extends over titaniumlocated on one surface of the first electrode layer 103 that is closerto the orientation control layer 104 so that the cross-sectional area ofsuch a region in the direction perpendicular to the thickness directiongradually increases in the direction away from the first electrode layer103 toward the piezoelectric layer 110.

Next, a method for manufacturing the ink jet head excluding the IC chipE of FIG. 3, i.e., the ink jet head including the pressure chambermember A, the actuator section B, the ink channel member C and thenozzle plate D illustrated in FIG. 4, will be described with referenceto FIG. 6 to FIG. 10.

As illustrated in FIG. 6( a), an adhesive layer 121, the first electrodelayer 103, the orientation control layer 104, the piezoelectric layer110, the second electrode layer 112, the vibration layer 111 and theintermediate layer 113 are deposited in this order on a substrate 120 bya sputtering method. Note that the adhesive layer 121 is similar to theadhesive layer 12 of Embodiment 1, and is formed between the substrate120 and the first electrode layer 103 in order to improve the adhesiontherebetween (it may not always be necessary to form the adhesive layer121). As will be described later, the adhesive layer 121 is subsequentlyremoved as is the substrate 120. Moreover, Cr is used as the material ofthe vibration layer 111, and Ti is used as the material of theintermediate layer 113.

A cut-out Si substrate having a size of 18 mm×18 mm is used as thesubstrate 120. The substrate 120 is not limited to an Si substrate, butmay alternatively be a glass substrate, a metal substrate, or a ceramicsubstrate. Moreover, the substrate size is not limited to 18 mm×18 mm,and a wafer having a diameter of 2 to 10 inches may be used as long asit is an Si substrate.

The adhesive layer 121 is obtained by using a Ti target and applying ahigh-frequency power of 100 W thereto for 1 minute while heating thesubstrate 120 to 400° C. in an argon gas at 1 Pa. The thickness of theadhesive layer 121 is 0.02 μm. Note that the material of the adhesivelayer 121 is not limited to Ti, but may alternatively be tantalum, iron,cobalt, nickel, chromium, or a compound thereof (including Ti).Moreover, the thickness is not limited to any particular thickness aslong as it is in the range of 0.005 to 0.2 μm.

The first electrode layer 103 was obtained by using a Ti target and a Pttarget and applying high-frequency powers of 85 W and 200 W thereto,respectively, for 12 minutes while heating the substrate 120 to 600° C.in an argon gas at 1 Pa, using a multi-target sputtering apparatus. Thefirst electrode layer 103 has a thickness of 0.2 μm, and is orientedalong the (111) plane. Moreover, the Ti content is 2.5 mol %. As is thefirst electrode layer 14 of Embodiment 1, the first electrode layer 103may be made of at least one noble metal selected from the groupconsisting of Pt, iridium, palladium and ruthenium to which titanium ortitanium oxide is added (the amount of the additive to be added ispreferably greater than zero and less than or equal to 30 mol %), andthe thickness thereof is not limited to any particular thickness as longas it is in the range of 0.05 to 2 μm.

The orientation control layer 104 is obtained by using a sinter targetprepared by adding a 15 mol % excess of lead oxide (PbO) to PLTcontaining 10 mol % of lanthanum and applying a high-frequency power of300 W thereto for 12 minutes while heating the substrate 120 to 600° C.in a mixed atmosphere of argon and oxygen (gas volume ratio: Ar:O₂=19:1)at a degree of vacuum of 0.8 Pa. The obtained lead lanthanum titanatefilm has a perovskite crystalline structure containing 10 mol % oflanthanum and containing lead 10% in excess of the stoichiometriccomposition, and is oriented along the (100) or (001) plane overtitanium located on one surface of the first electrode layer 103 that iscloser to the orientation control layer 104 so that the cross-sectionalarea of the (100)- or (001)-oriented region gradually increases in thedirection away from the first electrode layer 103 toward the other side(i.e., toward the piezoelectric layer 110). On the other hand, eachregion of the orientation control layer 104, which is located over aportion of the surface of the first electrode layer 103 where none oftitanium and titanium oxide exist, is not oriented along the (100) or(001) plane, but such a region gradually shrinks toward thepiezoelectric layer 110. In the present embodiment, the thickness of theorientation control layer 104 is 0.02 μm, whereby the (100)- or(001)-oriented region extends substantially across the entire surface ofthe orientation control layer 104 that is closer to the piezoelectriclayer 110.

Note that as with the orientation control layer 15 of Embodiment 1, theLa content of the orientation control layer 104 may be greater than zeroand less than or equal to 25 mol %, and the lead content thereof may bein excess of the stoichiometric composition by an amount greater thanzero and less than or equal to 30 mol %. Moreover, the material of theorientation control layer 104 may be PLZT obtained by adding zirconiumto PLT (the zirconium content is preferably 20 mol % or less), or may bea material obtained by adding at least one of magnesium and manganese toPLT or PLZT (the amount of magnesium and manganese to be added ispreferably greater than zero and less than or equal to 10 mol %).Moreover, the thickness of the orientation control layer 104 is notlimited to any particular thickness as long as it is in the range of0.01 to 0.2 μm.

The piezoelectric layer 110 is obtained by using a sinter target of PZT(Zr/Ti=52/48) and applying a high-frequency power of 250 W thereto for 3hours while heating the substrate 120 to 580° C. in a mixed atmosphereof argon and oxygen (gas volume ratio: Ar:O₂=15:1) at a degree of vacuumof 0.3 Pa. The obtained PZT film has a rhombohedral perovskitecrystalline structure, and is oriented along the (100) plane. Moreover,the thickness of the piezoelectric layer 110 is 3.1 μm. Note that theZr/Ti composition of the piezoelectric layer 110 is not limited to anyparticular composition as long as it is in the range of 30/70 to 70/30,and the thickness thereof is not limited to any particular thickness aslong as it is in the range of 1 to 5 nm. Moreover, the material of thepiezoelectric layer 110 is not limited to any particular material, aslong as it is a piezoelectric material whose main component is PZT,e.g., those obtained by adding an additive such as Sr, Nb or Al to PZT.For example, PMN or PZN may be used.

The second electrode layer 112 is obtained by using a Pt target andapplying a high-frequency power of 200 W thereto for 10 minutes at aroom temperature in an argon gas at 1 Pa. The thickness of the secondelectrode layer 112 is 0.2 μm. Note that the material of the secondelectrode layer 112 is not limited to Pt as long as it is a conductivematerial, and the thickness thereof is not limited to any particularthickness as long as it is in the range of 0.1 to 0.4 μm.

The vibration layer 111 is obtained by using a Cr target and applying ahigh-frequency power of 200 W thereto for 6 hours at a room temperaturein an argon gas at 1 Pa. The thickness of the vibration layer 111 is 3μm. The material of the vibration layer 111 is not limited to Cr, butmay alternatively be nickel, aluminum, tantalum, tungsten, silicon, oran oxide or nitride thereof (e.g., silicon dioxide, aluminum oxide,zirconium oxide, silicon nitride), etc. Moreover, the thickness of thevibration layer 111 is not limited to any particular thickness as longas it is in the range of 2 to 5 μm.

The intermediate layer 113 is obtained by using a Ti target and applyinga high-frequency power of 200 W thereto for 5 hours at a roomtemperature in an argon gas at 1 Pa. The thickness of the intermediatelayer 113 is 5 μm. The material of the intermediate layer 113 is notlimited to Ti, but may alternatively be any suitable conductive metalmaterial such as Cr. Moreover, the thickness of the intermediate layer113 is not limited to any particular thickness as long as it is in therange of 3 to 10 μm.

On the other hand, the pressure chamber member A is formed asillustrated in FIG. 6( b). The pressure chamber member A is formed byusing a substrate of a larger size than the Si substrate 120, e.g., a4-inch wafer silicon substrate 130 (see FIG. 11). Specifically, aplurality of pressure chamber cavities 101 are first formed bypatterning in the silicon substrate 130 (for forming the pressurechamber member). As can be seen from FIG. 6( b), in the patterningprocess, the width of a partition wall 102 b for partitioning pairs offour pressure chamber cavities 101 from one another is set to be abouttwice as large as that of the partition wall 102 a for partitioning thepressure chamber cavities 101 from one another in each pair. Then, thepatterned silicon substrate 130 is subjected to chemical etching, dryetching, or the like, to form four pressure chamber cavities 101 foreach pair, thereby obtaining the pressure chamber member A.

Thereafter, the silicon substrate 120 (for depositing films thereon)after the deposition process and the pressure chamber member A arebonded to each other with an adhesive. The application of the adhesiveis done by electrodeposition. Specifically, the adhesive 114 is firstapplied onto the bonding surface of the pressure chamber member A, i.e.,the upper surface of the pressure chamber partition walls 102 a and 102b, by electrodeposition, as illustrated in FIG. 6( c). Specifically,although not shown, an Ni thin film having a thickness on the order of100 Å such that light can pass therethrough is formed as a baseelectrode film on the upper surface of the partition walls 102 a and 102b by a sputtering method, and then a patterned layer of the adhesiveresin agent 114 is formed on the Ni thin film. In this process, theelectrodeposition solution may be a solution obtained by adding 0 to 50%by weight of pure water to an acrylic resin aqueous dispersion, followedby thorough stirring and mixing. The Ni thin film is so thin that lightcan pass therethrough, so that it can easily be visually observed thatthe adhesive resin has completely attached to the silicon substrate 130(for forming the pressure chamber member). Experimentally, preferredelectrodeposition conditions include a solution temperature of about 25°C., a DC voltage of 30 V, and a voltage application time of 60 seconds,and an acrylic resin layer having a thickness of about 3 to 10 μm iselectrodeposited under these conditions on the Ni thin film of thesilicon substrate 130 (for forming the pressure chamber member).

Then, as illustrated in FIG. 7( a), the Si substrate 120 (for depositingfilms thereon) after the deposition process and the pressure chambermember A are bonded to each other with the electrodeposited adhesive114. In the bonding process, the intermediate layer 113 deposited on thesubstrate 120 (for depositing films thereon) is used as thesubstrate-side bonding surface. Moreover, the Si substrate 120 (fordepositing films thereon) has a size of 18 mm, whereas the Si substrate130 for forming the pressure chamber member A is as large as 4 inches, aplurality (14 in the example illustrated in FIG. 11) of Si substrates120 (for depositing films thereon) are attached to a single pressurechamber member A (the Si substrate 130), as illustrated in FIG. 11. Theattachment is done while the center of each Si substrate 120 (fordepositing films thereon) is aligned with the center of the widepartition wall 102 b of the pressure chamber member A, as illustrated inFIG. 7( a). After the attachment, the pressure chamber member A ispressed against, and thus brought into close contact with, the Sisubstrate 120 (for depositing films thereon) so that they are bonded toeach other fluid-tightly. Furthermore, the Si substrate 120 (fordepositing films thereon) and the pressure chamber member A bonded toeach other are gradually heated in a heating furnace so as to completelyset the adhesive 114. Then, a plasma treatment is performed so as toremove excessive portions of the adhesive 114.

Note that although the Si substrate 120 (for depositing films thereon)after the deposition process and the pressure chamber member A arebonded to each other in FIG. 7( a), the Si substrate 130 (for formingthe pressure chamber member) before the formation of the pressurechamber cavities 101 may alternatively be bonded to the Si substrate 120(for depositing films thereon) after the deposition process.

Then, as illustrated in FIG. 7( b), the intermediate layer 113 is etchedinto a predetermined pattern using the partition walls 102 a and 102 bof the pressure chamber member A as a mask (so that remaining portionsof the intermediate layer 113 are continuous with the partition walls102 a and 102 b (thus forming vertical walls)). Then, as illustrated inFIG. 8( a), the Si substrate 120 (for depositing films thereon) and theadhesive layer 121 are removed by etching.

Then, as illustrated in FIG. 8( b), the first electrode layer 103located above the pressure chamber member A is etched by aphotolithography technique so that the first electrode layer 103 isdivided into portions each corresponding to one pressure chamber 102.Then, as illustrated in FIG. 9( a), the orientation control layer 104and the piezoelectric layer 110 are etched by a photolithographytechnique so as to be divided into portions arranged in a patternsimilar to that of the first electrode layer 103. The remaining portionsof the first electrode layer 103, the orientation control layer 104 andthe piezoelectric layer 110 after the etching process are located abovethe respective pressure chambers 102. The center of the width of each ofthe first electrode layer 103, the orientation control layer 104 and thepiezoelectric layer 110 precisely corresponds to the center of the widthof the corresponding pressure chamber 102. Thus, the first electrodelayer 103, the orientation control layer 104 and the piezoelectric layer110 are divided into portions each corresponding to one pressure chamber102, and then the silicon substrate 130 (for forming the pressurechamber member) is cut along the wide partition walls 102 b, therebyobtaining four sets of the pressure chamber member A, each includingfour pressure chambers 102, and the actuator section B fixed to theupper surface of the pressure chamber member A, as illustrated in FIG.9( b).

Then, as illustrated in FIG. 10( a), the common ink chamber 105, thesupply ports 106 and the ink channels 107 are formed in the ink channelmember C, and the nozzle holes 108 are formed in the nozzle plate D.Then, as illustrated in FIG. 10( b), the ink channel member C and thenozzle plate D are bonded together with an adhesive 109.

Then, as illustrated in FIG. 10( c), an adhesive (not shown) istransferred onto the lower surface of the pressure chamber member A orthe upper surface of the ink channel member C, and the pressure chambermember A and the ink channel member C are bonded together after they arealigned with each other. Through the process as described above, the inkjet head including the pressure chamber member A, the actuator sectionB, the ink channel member C and the nozzle plate D is completed, asillustrated in FIG. 10( d).

When a predetermined voltage is applied between the first electrodelayer 103 and the second electrode layer 112 of the ink jet headobtained as described above, the displacement occurs in the thicknessdirection of a portion of the vibration layer 111 corresponding to eachpressure chamber 102 due to the piezoelectric effect of thepiezoelectric layer 110, whereby ink in the pressure chamber 102 isdischarged through the nozzle hole 108 communicated to the pressurechamber 102. The displacement in the thickness direction of a portion ofthe vibration layer 111 corresponding to the pressure chamber 102 wasmeasured, indicating that the deviation in the displacement was σ=1.8%.Moreover, after applying a 20 V AC voltage having a frequency of 20 kHzfor 10 days, deterioration in the ink-discharge performance was notobserved with no ink-discharge defect.

On the other hand, an ink jet head similar to the ink jet head of thepresent invention was produced except only that the orientation controllayer 104 was not provided. The displacement in the thickness directionof a portion of the vibration layer 111 corresponding to the pressurechamber 102 was measured while applying a predetermined voltage betweenthe first electrode layer 103 and the second electrode layer 112 of theink jet head. The deviation in the displacement was σ=7.2%. Moreover,after applying a 20 V AC voltage having a frequency of 20 kHz for 10days, an ink-discharge defect was observed in locations corresponding toabout 30% of all the pressure chambers 102. This was not due to cloggingof ink, etc. It is therefore believed that the actuator section B (thepiezoelectric element) had a poor durability.

Thus, it can be seen that the ink jet head of the present embodiment hasa desirable durability with a small deviation in the ink-dischargeperformance.

EMBODIMENT 3

FIG. 12 illustrates an important part of another ink jet head accordingto an embodiment of the present invention. In the ink jet head of thepresent embodiment, a substrate is used both for depositing filmsthereon and for forming the pressure chamber member, rather than usingseparate substrates, one for depositing films thereon and another forforming the pressure chamber member, as in the ink jet head ofEmbodiment 2.

Specifically, a vibration layer 403, an adhesive layer 404, a firstelectrode layer 406 (common electrode), an orientation control layer407, a piezoelectric layer 408 and a second electrode layer 409(separate electrode) are layered in this order on a pressure chambersubstrate 401 (pressure chamber member) in which pressure chambers 402have been formed by an etching process. The first electrode layer 406,the orientation control layer 407, the piezoelectric layer 408 and thesecond electrode layer 409 are arranged in this order to form apiezoelectric element. Moreover, the vibration layer 403 is provided onone surface of the piezoelectric element that is closer to the firstelectrode layer 406 via the adhesive layer 404. The adhesive layer 404is provided for improving the adhesion between the vibration layer 403and the first electrode layer 406, and may be omitted as the adhesivelayer 121 of Embodiment 2. The materials of the adhesive layer 404, thefirst electrode layer 406, the orientation control layer 407, thepiezoelectric layer 408 and the second electrode layer 409 are similarto those of the adhesive layer 121, the first electrode layer 103, theorientation control layer 104, the piezoelectric layer 110 and thesecond electrode layer 112, respectively, of Embodiment 2. Moreover, thestructures of the orientation control layer 407 and the piezoelectriclayer 408 are similar to those of the orientation control layer 104 andthe piezoelectric layer 110, respectively. In the vicinity of onesurface of the orientation control layer 407 that is closer to the firstelectrode layer 406, a (100)- or (001)-oriented region extends overtitanium located on one surface of the first electrode layer 406 that iscloser to the orientation control layer 407 so that the cross-sectionalarea of such a region in the direction perpendicular to the thicknessdirection gradually increases in the direction away from the firstelectrode layer 406 toward the piezoelectric layer 408.

An Si substrate having a diameter of 4 inches and a thickness of 200 μmis used as the pressure chamber substrate 401. Also in this embodiment,the substrate 401 is not limited to an Si substrate, but mayalternatively be a glass substrate, a metal substrate, or a ceramicsubstrate.

In the present embodiment, the vibration layer 403 has a thickness of2.8 μm and is made of silicon dioxide. Note that the material of thevibration layer 403 is not limited to silicon dioxide, but mayalternatively be any of those mentioned in Embodiment 2 (nickel,chromium, etc., or an oxide or nitride thereof). Moreover, the thicknessof the vibration layer 111 is not limited to any particular thickness aslong as it is in the range of 0.5 to 10 μm.

Next, a method for manufacturing the ink jet head as described abovewill be described with reference to FIG. 13.

First, as illustrated in FIG. 13( a), the vibration layer 403, theadhesive layer 404, the first electrode layer 406, the orientationcontrol layer 407, the piezoelectric layer 408 and the second electrodelayer 409 are formed in this order by a sputtering method on thepressure chamber substrate 401 on which the pressure chambers 402 havenot been formed.

The vibration layer 403 is obtained by using a silicon dioxide sintertarget and applying a high-frequency power of 300 W thereto for 8 hoursat a room temperature without heating the pressure chamber substrate 401in a mixed atmosphere of argon and oxygen at 0.4 Pa (gas volume ratio:Ar:O₂=5:25). Note that deposition method for the vibration layer 403 isnot limited to a sputtering method, but may alternatively be a thermalCVD method, a plasma CVD method, a sol-gel method, or the like, or itmay alternatively be formed through a thermal oxidization process on thepressure chamber substrate 401.

The adhesive layer 404 is obtained by using a Ti target and applying ahigh-frequency power of 100 W thereto for 1 minute while heating thepressure chamber substrate 401 to 400° C. in an argon gas at 1 Pa. Thethickness of the adhesive layer 404 is 0.03 μm. Note that the materialof the adhesive layer 404 is not limited to Ti, but may alternatively betantalum, iron, cobalt, nickel, chromium, or a compound thereof(including Ti). Moreover, the thickness is not limited to any particularthickness as long as it is in the range of 0.005 to 0.1 μm.

The first electrode layer 406 was obtained by using a Ti target and a Pttarget and applying high-frequency powers of 85 W and 200 W thereto,respectively, for 12 minutes while heating the pressure chambersubstrate 401 to 600° C. in an argon gas at 1 Pa, using a multi-targetsputtering apparatus. The first electrode layer 406 has a thickness of0.2 μm, and is oriented along the (111) plane. Moreover, the Ti contentis 2.5 mol %. As is the first electrode layer 14 of Embodiment 1, thefirst electrode layer 406 may be made of at least one noble metalselected from the group consisting of Pt, iridium, palladium andruthenium to which titanium or titanium oxide is added (the amount ofthe additive to be added is preferably greater than zero and less thanor equal to 30 mol %), and the thickness thereof is not limited to anyparticular thickness as long as it is in the range of 0.05 to 2 μm.

The orientation control layer 407 is obtained by using a sinter targetprepared by adding a 15 mol % excess of lead oxide (PbO) to PLTcontaining 10 mol % of lanthanum and applying a high-frequency power of300 W thereto for 12 minutes while heating the pressure chambersubstrate 401 to 620° C. in a mixed atmosphere of argon and oxygen (gasvolume ratio: Ar:O₂=19:1) at a degree of vacuum of 0.8 Pa. The obtainedlead lanthanum titanate film is the same as the orientation controllayer 104 of Embodiment 2.

Note that as with the orientation control layer 15 of Embodiment 1, theLa content of the orientation control layer 407 may be greater than zeroand less than or equal to 25 mol %, and the lead content thereof may bein excess of the stoichiometric composition by an amount greater thanzero and less than or equal to 30 mol %. Moreover, the material of theorientation control layer 407 may be PLZT obtained by adding zirconiumto PLT (the zirconium content is preferably 20 mol % or less), or may bea material obtained by adding at least one of magnesium and manganese toPLT or PLZT (the amount of magnesium and manganese to be added ispreferably greater than zero and less than or equal to 10 mol %).Moreover, the thickness of the orientation control layer 104 is notlimited to any particular thickness as long as it is in the range of0.01 to 0.2 μm.

The piezoelectric layer 408 is obtained by using a sinter target of PZT(Zr/Ti=52/48) and applying a high-frequency power of 250 W thereto for 3hours while heating the pressure chamber substrate 401 to 580° C. in amixed atmosphere of argon and oxygen (gas volume ratio: Ar:O₂=15:1) at adegree of vacuum of 0.3 Pa. The obtained PZT film is the same as thepiezoelectric layer 110 of Embodiment 2. Note that the Zr/Ti compositionof the piezoelectric layer 408 is not limited to any particularcomposition as long as it is in the range of 30/70 to 70/30, and thethickness thereof is not limited to any particular thickness as long asit is in the range of 1 to 5 μm. Moreover, the material of thepiezoelectric layer 408 is not limited to any particular material, aslong as it is a piezoelectric material whose main component is PZT,e.g., those obtained by adding an additive such as Sr, Nb or Al to PZT.For example, PMN or PZN may be used.

The second electrode layer 409 is obtained by using a Pt target andapplying a high-frequency power of 200 W thereto for 10 minutes at aroom temperature in an argon gas at 1 Pa. The thickness of the secondelectrode layer 409 is 0.2 μm. Note that the material of the secondelectrode layer 409 is not limited to Pt as long as it is a conductivematerial, and the thickness thereof is not limited to any particularthickness as long as it is in the range of 0.1 to 0.4 μm.

Then, a resist is applied by a spin coating method on the secondelectrode layer 409, and then patterned through exposure and developmentprocesses into a pattern corresponding to the pressure chambers 402 tobe formed. Then, the second electrode layer 409, the piezoelectric layer408 and the orientation control layer 407 are divided into portions byetching. The etching process is a dry etching process using a mixed gasof argon and an organic gas including fluorine element.

Then, as illustrated in FIG. 13( b), the pressure chambers 402 areformed in the pressure chamber substrate 401. The pressure chambers 402are formed by an anisotropic dry etching process using a sulfurhexafluoride gas, an organic gas including fluorine element, or a mixedgas thereof. Specifically, the pressure chambers 402 are formed byperforming an anisotropic dry etching after forming an etching mask onone surface of the pressure chamber substrate 401 that is opposite tothe other surface thereof on which various films have been formed so asto cover each portion thereof corresponding to a side wall 413 to beformed.

Then, a nozzle plate 412 with nozzle holes 410 formed therein is bondedto the surface of the pressure chamber substrate 401 that is opposite tothe other surface thereof on which various films have been formed,thereby obtaining the ink jet head. The nozzle holes 410 are opened atpredetermined positions in the nozzle plate 412 by a photolithographymethod, a laser processing method, an electrical discharge machiningmethod, or the like. Then, before the nozzle plate 412 is bonded to thepressure chamber substrate 401, they are aligned with each other so thatthe nozzle holes 410 correspond to the pressure chambers 402,respectively.

The displacement in the thickness direction of a portion of thevibration layer 403 corresponding to the pressure chamber 402 wasmeasured while applying a predetermined voltage between the firstelectrode layer 406 and the second electrode layer 409 of an ink jethead obtained as described above. The deviation in the displacement wasσ32 1.8%. Moreover, after applying a 20 V AC voltage having a frequencyof 20 kHz for 10 days, deterioration in the ink-discharge performancewas not observed with no ink-discharge defect.

On the other hand, an ink jet head similar to the ink jet head of thepresent invention was produced except only that the orientation controllayer 407 was not provided. The displacement in the thickness directionof a portion of the vibration layer 403 corresponding to the pressurechamber 402 was measured while applying a predetermined voltage betweenthe first electrode layer 406 and the second electrode layer 409 of theink jet head. The deviation in the displacement was σ=5.8%. Moreover,after applying a 20 V AC voltage having a frequency of 20 kHz for 10days, an ink-discharge defect was observed in locations corresponding toabout 25% of all the pressure chambers 402. This was not due to cloggingof ink, etc. It is therefore believed that the actuator section (thepiezoelectric element) had a poor durability.

Thus, it can be seen that the ink jet head of the present embodiment hasa desirable durability and a small deviation in the ink-dischargeperformance, as the ink jet head of Embodiment 2.

EMBODIMENT 4

FIG. 14 illustrates an ink jet recording apparatus 27 according to anembodiment of the present invention. The ink jet recording apparatus 27includes an ink jet head 28, which is similar to the ink jet head ofEmbodiment 2 or 3. The ink jet head 28 is configured so that ink in eachpressure chamber (the pressure chamber 102 of Embodiment 2 or thepressure chamber 402 of Embodiment 3) is discharged through a nozzlehole (the nozzle hole 108 of Embodiment 2 or the nozzle hole 410 ofEmbodiment 3), which is communicated to the pressure chamber, onto arecording medium 29 (e.g., recording paper) for recording information.

The ink jet head 28 is mounted on a carriage 31, which is provided on acarriage shaft 30 extending in the primary scanning direction X, and isreciprocated in the primary scanning direction X as the carriage 31reciprocates along the carriage shaft 30. Thus, the carriage 31 formsrelative movement means for relatively moving the ink jet head 28 andthe recording medium 29 with respect to each other in the primaryscanning direction X.

Moreover, the ink jet recording apparatus 27 includes a plurality ofrollers 32 for moving the recording medium 29 in the secondary scanningdirection Y, which is substantially perpendicular to the primaryscanning direction X (width direction) of the ink jet head 28. Thus, theplurality of rollers 32 together form relative movement means forrelatively moving the ink jet head 28 and the recording medium 29 withrespect to each other in the secondary scanning direction Y. Note thatin FIG. 14, arrow Z represents the vertical direction.

While the ink jet head 28 is moved by the carriage 31 from one side tothe other in the primary scanning direction X, ink is discharged throughthe nozzle holes of the ink jet head 28 onto the recording medium 29.After one scan of recording operation, the recording medium 29 is movedby the rollers 32 by a predetermined amount, and then the next scan ofrecording operation is performed.

Since the ink jet recording apparatus 27 includes the ink jet head 28similar to that of Embodiment 2 or 3, the ink jet recording apparatus 27provides a desirable printing performance and durability.

EMBODIMENT 5

FIG. 15 and FIG. 16 illustrate an angular velocity sensor according toan embodiment of the present invention. The angular velocity sensor hasa shape of a tuning fork, and can suitably be used in a vehicle-mountednavigation system, or the like.

The angular velocity sensor includes a substrate 500 made of a siliconwafer having a thickness of 0.3 mm (the substrate 500 may alternativelybe a glass substrate, a metal substrate or a ceramic substrate). Thesubstrate 500 includes a fixed portion 500 a, and a pair of vibratingportions 500 b extending from the fixed portion 500 a in a predetermineddirection (the direction of the rotation axis with respect to which theangular velocity is to be detected; the y direction in FIG. 15 in thepresent embodiment). The fixed portion 500 a and the pair of vibratingportions 500 b together form a shape of a tuning fork as viewed in thethickness direction of the substrate 500 (the z direction in FIG. 15),and the pair of vibrating portions 500 b, corresponding to the arms of atuning fork, extend in parallel to each other while being arranged nextto each other in the width direction of the vibrating portions 500 b.

A first electrode layer 503, an orientation control layer 504, apiezoelectric layer 505 and a second electrode layer 506 are layered inthis order on the vibrating portions 500 b of the substrate 500 and aportion of the fixed portion 500 a close to the vibrating portions 500b. Note that also in the angular velocity sensor, it is preferred thatan adhesive layer is provided between the substrate 500 and the firstelectrode layer 503, as in the piezoelectric element of Embodiment 1.

The materials and the thicknesses of the first electrode layer 503, theorientation control layer 504, the piezoelectric layer 505 and thesecond electrode layer 506 are similar to those of the first electrodelayer 14, the orientation control layer 15, the piezoelectric layer 16and the second electrode layer 17, respectively, of Embodiment 1.Moreover, the structures of the orientation control layer 504 and thepiezoelectric layer 505 are similar to those of the orientation controllayer 15 and the piezoelectric layer 16, respectively. In the vicinityof one surface of the orientation control layer 504 that is closer tothe first electrode layer 503, a (100)- or (001)-oriented region extendsover titanium located on one surface of the first electrode layer 503that is closer to the orientation control layer 504 so that thecross-sectional area of such a region in the direction perpendicular tothe thickness direction gradually increases in the direction away fromthe first electrode layer 503 toward the piezoelectric layer 505.

On each vibrating portion 500 b, the second electrode layer 506 ispatterned into three portions, i.e., two driving electrodes 507 forvibrating the vibrating portion 500 b in the width direction thereof(the x direction in FIG. 15), and a detection electrode 508 fordetecting a displacement (deflection) of the vibrating portion 500 b inthe thickness direction thereof (the z direction).

The two driving electrodes 507 extend along the lateral edges of thevibrating portion 500 b that are opposing each other with respect to thewidth direction thereof (the x direction) and entirely across thevibrating portion 500 b in the longitudinal direction thereof (the ydirection). One end of each driving electrode 507 that is closer to thefixed portion 500 a forms a connection terminal 507 a on the fixedportion 500 a. Note that only one driving electrode 507 mayalternatively be provided on one of the opposite edges of each vibratingportion 500 b.

On the other hand, the detection electrode 508 extends in the centralportion of the vibrating portion 500 b with respect to the widthdirection thereof and entirely across the vibrating portion 500 b in thelongitudinal direction thereof. As does the driving electrode 507, oneend of the detection electrode 508 that is closer to the fixed portion500 a forms a connection terminal 508 a on the fixed portion 500 a. Notethat a plurality of detection electrodes 508 may alternatively beprovided on each vibrating portion 500 b.

Note that the first electrode layer 503 forms a connection terminal 503a, extending away from the vibrating portion 500 b, on the fixed portion500 a between the pair of vibrating portions 500 b.

Applied between the first electrode layer 503 and the two drivingelectrodes 507 on the vibrating portion 500 b is a voltage having afrequency that is resonant with the proper oscillation of the vibratingportion 500 b so that the vibrating portion 500 b vibrates in the widthdirection thereof. Specifically, two voltages of opposite polarity areapplied to the two driving electrodes 507 while the ground voltage isapplied to the first electrode layer 503, whereby when one lateral edgeof the vibrating portion 500 b expands, the other lateral edgecontracts, and thus the vibrating portion 500 b deforms toward thesecond lateral edge. On the other hand, when the first lateral edge ofthe vibrating portion 500 b contracts, the second lateral edge expands,and thus the vibrating portion 500 b deforms toward the first lateraledge. By repeating this operation, the vibrating portion 500 b vibratesin the width direction thereof. Note that by applying a voltage to onlyone of the two driving electrodes 500 b on each vibrating portion 500 b,the vibrating portion 500 b can be vibrated in the width directionthereof. The pair of vibrating portions 500 b are configured so thatthey deform in opposite directions with respect to the width directionthereof and in symmetry with each other with respect to the center lineL, which extends in the longitudinal direction of the vibrating portion500 b between the pair of vibrating portions 500 b.

In the angular velocity sensor having such a configuration, if anangular velocity ω about the center line L is applied while the pair ofvibrating portions 500 b are being vibrated in the width directionthereof (the x direction) symmetrically with respect to the center lineL, the two vibrating portions 500 b are bent and deformed in thethickness direction (the z direction) by the Coriolis force (the pair ofvibrating portions 500 b are bent by the same amount but in oppositedirections), thereby also bending the piezoelectric layer 505, and thusgenerating a voltage according to the magnitude of the Coriolis forcebetween the first electrode layer 503 and the detection electrode 508.Then, the angular velocity ω can be calculated based on the magnitude ofthe voltage (the Coriolis force).

The Coriolis force Fc is expressed as follows:Fc=2mvω,

-   -   where v denotes the velocity of each vibrating portion 500 b in        the width direction, and m denotes the mass of each vibrating        portion 500 b.        Thus, the value of the angular velocity co can be obtained from        the Coriolis force Fc.

Next, a method for manufacturing the angular velocity sensor will bedescribed with reference to FIG. 17 and FIG. 18.

As illustrated in FIG. 17( a), the substrate 500 made of a 4-inchsilicon wafer having a thickness of 0.3 mm is provided (see the planview of FIG. 18). Then, as illustrated in FIG. 17( b), the firstelectrode layer 503 is formed of iridium (Ir) to which 2.1 mol % of Tiis added on the substrate 500 by a sputtering method so as to have athickness of 0.22 μm. The first electrode layer 503 is obtained by usinga Ti target and a Pt target and applying high-frequency powers of 85 Wand 200 W thereto, respectively, for 12 minutes while heating thesubstrate 500 to 400° C. in an argon gas at 1 Pa, using a multi-targetsputtering apparatus. Titanium exists in a dotted pattern on a surfaceof the first electrode layer 503, and the titanium protrudes less than 2nm from the surface.

Then, as illustrated in FIG. 17( c), the orientation control layer 504is formed on the first electrode layer 503 by a sputtering method so asto have a thickness of 0.03 μm. The orientation control layer 504 isobtained by using a sinter target prepared by adding a 12 mol % excessof lead oxide (PbO) to PLT containing 14 mol % of lanthanum and applyinga high-frequency power of 300 W thereto for 12 minutes while heating thesubstrate 500 to 600° C. in a mixed atmosphere of argon and oxygen (gasvolume ratio: Ar:O₂=19:1) at a degree of vacuum of 0.8 Pa. According tothis production method, as described above in Embodiment 1, in thevicinity of one surface of the orientation control layer 504 that iscloser to the first electrode layer 503, a (100)- or (001)-orientedregion extends over titanium so that the cross-sectional area of theregion in the direction perpendicular to the thickness directiongradually increases in the upward direction away from the firstelectrode layer 503.

Then, as illustrated in FIG. 17( d), the piezoelectric layer 505 isformed on the orientation control layer 504 by a sputtering method so asto have a thickness of 3 μm. The piezoelectric layer 505 is obtained byusing a sinter target of PZT (Zr/Ti=53/47) and applying a high-frequencypower of 250 W thereto for 3 hours while heating the substrate 500 to610° C. in a mixed atmosphere of argon and oxygen (gas volume ratio:Ar:O₂=19:1) at a degree of vacuum of 0.3 Pa. The piezoelectric layer 505is rhombohedral, with the degree of (001) orientation thereof being 90%or more, as described in Embodiment 1.

Then, as illustrated in FIG. 17( e), the second electrode layer 506 isformed on the piezoelectric layer 505 by a sputtering method so as tohave a thickness of 0.2 μm. The second electrode layer 506 is obtainedby using a Pt target and applying a high-frequency power of 200 Wthereto for 10 minutes at a room temperature in an argon gas at 1 Pa.

Then, as illustrated in FIG. 17( f) and FIG. 18, the second electrodelayer 506 is patterned so as to form the driving electrodes 507 and thedetection electrode 508. Specifically, a photosensitive resin is appliedon the second electrode layer 506 and is exposed to light to form thepattern of the driving electrodes 507 and the detection electrode 508,and the unexposed portions of the photosensitive resin are removed. Thesecond electrode layer 506 is etched and removed in locations where thephotosensitive resin has been removed. Then, the photosensitive resin onthe driving electrodes 507 and the detection electrode 508 is removed.

After patterning the second electrode layer 506, the piezoelectric layer505, the orientation control layer 504 and the first electrode layer 503are patterned in similar steps, and the substrate 500 is patterned,thereby forming the fixed portion 500 a and the vibrating portions 500b. Thus, the angular velocity sensor is obtained.

Note that the deposition method for the various layers is not limited toa sputtering method, but may alternatively be any other suitabledeposition method as long as a crystalline thin film is directly formedwithout the crystallization step using a heat treatment (e.g., a CVDmethod).

Now, a conventional angular velocity sensor will be described withreference to FIG. 19 and FIG. 20.

The conventional angular velocity sensor includes a piezoelectric member600 made of quartz having a thickness of 0.3 mm. As does the substrate500 of the angular velocity sensor of the present embodiment, thepiezoelectric member 600 includes a fixed portion 600 a, and a pair ofvibrating portions 600 b extending from the fixed portion 600 a in onedirection (the y direction in FIG. 19) in parallel to each other. Thedriving electrodes 603 for vibrating the vibrating portion 600 b in thewidth direction thereof (the x direction in FIG. 19) are providedrespectively on two surfaces of the vibrating portion 600 b opposingeach other in the thickness direction thereof (the z direction in FIG.19), and detection electrodes 607 for detecting the displacement of thevibrating portion 600 b in the thickness direction are providedrespectively on two side surfaces of the vibrating portion 600 b.

In the conventional angular velocity sensor, a voltage having afrequency that is resonant with the proper oscillation of the vibratingportion 600 b is applied between the two driving electrodes 603 of eachvibrating portion 600 b so as to vibrate the pair of vibrating portions600 b in the width direction thereof (the x direction) symmetricallywith respect to the center line L between the pair of vibrating portions600 b, as in the angular velocity sensor of the present embodiment. Ifan angular velocity ω about the center line L is applied in this state,the pair of vibrating portions 600 b are bent and deformed in thethickness direction (the z direction) by the Coriolis force, therebygenerating a voltage according to the magnitude of the Coriolis forcebetween the two the detection electrodes 607 of each vibrating portion600 b. Then, the angular velocity ω can be calculated based on themagnitude of the voltage (the Coriolis force).

Since the conventional angular velocity sensor uses the piezoelectricmember 600 made of quartz, the piezoelectric constant is as low as −3pC/N. Moreover, since the fixed portion 600 a and the vibrating portion600 b are machined, it is difficult to reduce the size thereof, and thedimensional precision thereof is low.

In contrast, in the angular velocity sensor of the present embodiment,the portion for detecting the angular velocity (the vibrating portion500 b) is the piezoelectric element having a similar structure to thatof Embodiment 1. Therefore, the piezoelectric constant can be increasedto be about 40 times as large as that of the conventional angularvelocity sensor, and thus the size thereof can be reduced significantly.Moreover, minute processing with thin film formation techniques can beused, thereby significantly improving the dimensional precision.Furthermore, even if the angular velocity sensors are mass-producedindustrially, it is possible to obtain angular velocity sensors with ahigh characteristics reproducibility and a small characteristicsdeviation, and with a high breakdown voltage and a high reliability.

Note that also in the angular velocity sensor of the present embodiment,as in the piezoelectric element of Embodiment 1, the orientation controllayer 504 is preferably made of lead lanthanum zirconate titanate whosezirconium content is equal to or greater than zero and less than orequal to 20 mol % and whose lead content is in excess of thestoichiometric composition by an amount greater than zero and less thanor equal to 30 mol %, or made of the lead lanthanum zirconate titanateto which at least one of magnesium and manganese is added. The lanthanumcontent of the lead lanthanum zirconate titanate is preferably greaterthan zero and less than or equal to 25 mol %. When at least one ofmagnesium and manganese is added to the lead lanthanum zirconatetitanate, the total amount thereof to be added is preferably greaterthan zero and less than or equal to 10 mol %.

Moreover, the first electrode layer 503 is desirably made of at leastone noble metal selected from the group consisting of platinum, iridium,palladium and ruthenium, which contains titanium or titanium oxide. Thecontent of titanium or titanium oxide contained in the noble metal isdesirably greater than zero and less than or equal to 30 mol %.

Furthermore, the piezoelectric layer 505 is desirably made of apiezoelectric material whose main component is PZT (the piezoelectricmaterial may be composed only of PZT).

Furthermore, while only one pair of vibrating portions 500 b is providedin the substrate 500 in the angular velocity sensor of the presentembodiment, a plurality of pairs of vibrating portions may alternativelybe provided so as to detect angular velocities with respect to aplurality of axes extending in different directions.

Moreover, while the first electrode layer 503, the orientation controllayer 504, the piezoelectric layer 505 and the second electrode layer506 are layered in this order on the vibrating portions 500 b of thesubstrate 500 and a portion of the fixed portion 500 a close to thevibrating portions 500 b in the angular velocity sensor of the presentembodiment, these layers may alternatively be layered only on thevibrating portions 500 b.

In addition, while the piezoelectric element of the present invention isapplied to an ink jet head (an ink jet recording apparatus) and anangular velocity sensor in the embodiments described above, thepiezoelectric element of the present invention may be used in variousother applications including, but not limited to, thin film condensers,charge storage capacitors of non-volatile memory devices, various kindsof actuators, infrared sensors, ultrasonic sensors, pressure sensors,acceleration sensors, flow meters, shock sensors, piezoelectrictransformers, piezoelectric igniters, piezoelectric speakers,piezoelectric microphones, piezoelectric filters, piezoelectric pickups,tuning-fork oscillators, and delay lines. Particularly, thepiezoelectric element of the present invention may suitably be used in athin film piezoelectric actuator for a disk apparatus provided in a headsupporting mechanism, in which a head for recording or reproducinginformation to/from a disk being spun in a disk apparatus (a diskapparatus used as a storage device of a computer, etc.) is provided on asubstrate, wherein the substrate is deformed and the head is displacedby a thin film piezoelectric element provided on the substrate (see, forexample, Japanese Unexamined Patent Publication No. 2001-332041). Thethin film piezoelectric element has a similar structure to thatdescribed in the embodiments above, in which the first electrode layer,the orientation control layer, the piezoelectric layer and the secondelectrode layer are layered in this order, with the second electrodelayer being bonded to the substrate.

INDUSTRIAL APPLICABILITY

A piezoelectric element of the present invention possesses highindustrial applicability in respect that it is useful for variousactuators, such as an ink-discharge actuator in an ink jet head of anink jet recording apparatus, or the like, and for various sensors, suchas a tuning fork-shaped angular velocity sensor, or the like, and that ahighly-reliable piezoelectric element having superior piezoelectriccharacteristics is realized at a low cost.

1. A piezoelectric element, comprising: a first electrode layer providedon a substrate; an orientation control layer provided on the firstelectrode layer; a piezoelectric layer provided on the orientationcontrol layer; and a second electrode layer provided on thepiezoelectric layer, wherein the first electrode layer is made of anoble metal containing titanium or titanium oxide, the orientationcontrol layer is made of a cubic or tetragonal perovskite oxide that ispreferentially oriented along a (100) or (001) plane, the piezoelectriclayer is made of a rhombohedral or tetragonal perovskite oxide that ispreferentially oriented along a (001) plane, and in the vicinity of onesurface of the orientation control layer that is closer to the firstelectrode layer, a (100)- or (001)-oriented region extends over titaniumor titanium oxide located on one surface of the first electrode layerthat is closer to the orientation control layer, and the cross-sectionalarea of the (100)- or (001)-oriented region in the directionperpendicular to the thickness direction gradually increases in thedirection away from the first electrode layer toward the piezoelectriclayer.
 2. A piezoelectric element according to claim 1, wherein theorientation control layer is made of lead lanthanum zirconate titanatewhose zirconium content is equal to or greater than zero and less thanor equal to 20 mol % and whose lead content is in excess of thestoichiometric composition by an amount greater than zero and less thanor equal to 30 mol %, or made of the lead lanthanum zirconate titanateto which at least one of magnesium and manganese is added.
 3. Apiezoelectric element according to claim 2, wherein the lanthanumcontent of the lead lanthanum zirconate titanate is greater than zeroand less than or equal to 25 mol %.
 4. A piezoelectric element accordingto claim 2, wherein when at least one of magnesium and manganese isadded to the lead lanthanum zirconate titanate, the total amount thereofto be added is greater than zero and less than or equal to 10 mol %. 5.A piezoelectric element according to claim 1, wherein the firstelectrode layer is made of at least one noble metal selected from thegroup consisting of platinum, iridium, palladium and ruthenium, and thecontent of the titanium or titanium oxide which is contained in thenoble metal is greater than zero and less than or equal to 30 mol %. 6.A piezoelectric element according to claim 1, wherein titanium ortitanium oxide existing at a surface of the first electrode layer thatis closer to the orientation control layer protrudes less than 2 nm fromthe surface.
 7. A piezoelectric element according to claim 1, whereinthe piezoelectric layer is made of a piezoelectric material whose maincomponent is lead zirconate titanate.
 8. A piezoelectric elementaccording to claim 1, wherein an adhesive layer for improving adhesionbetween the substrate and the first electrode layer is provided betweenthe substrate and the first electrode layer.